It is not yet clear where the plane was taken, however Mr Razak said the most recent satellite data suggests the plane could have headed to one of two possible flight corridors.
The last radar contact was made at 8.11am on March 8 along one of the corridors, seven hours and 31 minutes after take off, but the plane could have deviated further from these points.
U.S. investigators have not ruled out the possibility that the passengers are being held at an unknown location and suggest that faint 'pings' were being transmitted for several hours after the flight lost contact with the ground.
NASA has also joined the international search operation, analysing satellite data and images that have already been gathered.
Malaysian authorities and others are urgently investigating the two pilots and 10 crew members, along with the 227 passengers on board.
WHY DIDN'T RADAR FIND THE PLANE?
Radar coverage of the area where flight MH370 went missing is patchy and often not even switched on, according to aviation experts.
It has emerged today that civilian systems do not cover large swatches of the areas the plane could have gone, and that military systems are often left off to save money.
Air Vice Marshal Michael Harwood, a former RAF pilot, said: ‘Too many movies and Predator [drone] feeds from Afghanistan have suckered people into thinking we know everything and see everything.
‘You get what you pay for. And the world, by and large, does not pay.'
Air traffic control teams rely transponders signals to track planes- but investigators believe that the device was intentionally switched off on the missing aircraft.
Military systems, meanwhile, are often limited, switched off , or routinely ignore aircraft they do not think are suspicious.
A Rear Admiral in the Indian armed forces, which are aiding search efforts over the Andaman Islands, said: ‘It's possible that the military radars were switched off as we operate on an "as required" basis.’
However, experts have suggested that a disappearing transponder signal would be treated more seriously over Europe or America, and that a parallel situation would be unlikely to develop.
Today, a police van with a large contingent of officers inside passed through a security gate at the entrance to the wealthy compound where father-of-three Captain Zaharie Ahmad Shah lives with his wife Faisa.
Four plain-clothed police officers were also, reportedly, seen at the home of the other pilot Fariq Abdul Hamid, 27.
Both pilots live in the upmarket Kuala Lumpur district of Laman Seri, about an hour's drive from the city centre - and each was visited today by a team of detectives who arrived in a white 'people mover' vehicle.
The homes are substantial and are, said one resident, typical of high income earners.
It is believed a team of search specialists entered Shah's house and spent two hours searching for signs of foul play, before moving into search the co-pilot's home a short distance away.
The New Straits Times reported last night that before police turned up at Hamid's home, his two brothers arrived there in a Mini Cooper, believed to belong to a friend.
They hurried into the house and remained there for a short time before hurrying away in the same car, taking with them transparent blue plastic bags containing clothes and toiletries.
Hamid's father, Abdul Hamid left with them. An hour later, the plain clothed officers left the house carrying two brown bags.
The concentration by police on the homes of the Captain and the co-pilot adds to suspicion that one - or both - of them might have had been responsible for the plight of the aircraft.
However, if it was diverted into the Indian Ocean, the task of the search teams becomes more difficult, as there are hundreds of uninhabited islands and the water reaches depths of around 23,000ft.
The maximum range of the Boeing 777-200ER is 7,725 nautical miles or 14,305 km.
It is not clear how much fuel the aircraft was carrying though it would have been enough to reach its scheduled destination, Beijing, a flight of five hours and 50 minutes, plus some reserve.
Experts have previously said that whoever disabled the plane's communication systems and then flew the jet must have had a high degree of technical knowledge and flying experience.
In Shah's house a flight simulator has been set up and is understood to have interested police following up one line of investigation - that he had used the equipment to practice making his real-life Boeing 777 ‘invisible’ by turning off all communications.
Malaysian Prime Minister Najib Razak (centre) on refused to confirm reports the plane was 'hijacked'
Another relative gives a statement to the media following the press conference
CHILD VICTIMS CAUGHT UP IN BAFFLING AVIATION MYSTERY
Among those lost on flight MH370 are children as young as two years old. Fears are mounting for the 239 people lost on board.
Photographs which emerged in the wake of the disappearance show a little girl, three, who was vocally adored by her parents online, and another, two, on the way home from his first ever holiday.
Wang Moheng, the plane's youngest passenger, was not even two when he flew to Malaysia from Beijing with his parents and grandparents.
Wang Moheng, two, (left) was coming home from holiday. Hu Siwan, three, (right) was adored online
They were headed on holiday to escape smog and bad weather in the Chinese city, and were on their way home when the plane vanished.
A parent whose child attended nursery with Moheng told the New York Times: 'They said to other parents at our day-care centre: "We're getting away from the bad air in Beijing for a while"'.
Hu Siwan, three, can be seen on a profile from the Chinese social network, Weibo. Her mother's profile shows an exchange where her father says 'Daddy... is so blissful to have you!' and 'Let us live together, happily ever after!', according to the Straits Times. The three live together in Beijing.
Despite the investigation, Malaysian officials and friends of the pilots have told MailOnline this week that there are no reasons to suspect either the captain or co-pilot of having personal problems that would have resulted in them taking control of the aircraft.
During his statement Mr Naqib added authorities have not ruled out any possibilities in the international search for the plane, which now involves 14 countries, 43 ships and 58 aircraft.
'Clearly the search has entered a new phase. Over the last seven days, we have followed every lead and looked into every possibility,' Mr Razak said. 'For family and friends (of the passengers), we hope this new information brings us one step closer to finding the plane.'
Mr Najib said data showed that the jet went north of the Straits of Malacca which resulted in the search to the north and later to the Andaman Sea.
'Investigation authorities have briefed me on what happened to the flight. Based on new satellite communication, with a high degree of certainty, we can say that the aircraft's communication system was disabled.
'Shortly afterwards, near the border between Malaysia and Vietnamese air space, the plane's transponder was switched off.
'Malaysia Airforce data showed that an aircraft believed to be MH370 flew in the opposite direction.
'These movements are consistent with deliberate action from someone on the plane.'
THE TWO PILOTS UNDER SUSPICION: A 'GOOD MUSLIM BOY' AND A FATHER DEDICATED TO COMMUNITY SERVICE
Suspicions: Jonti Roos (left) claims she and her friend were entertained by Fariq Abdul Hamid, 27, who is one of the pilots of the missing Malaysia Airlines flight (right). He is now part of an investigation by police in Kuala Lumpur
Following the confirmation that flight MH370 was hijacked, police raided the homes of Capt. Zaharie Ahmad Shah, 53, and his co-pilot Fariq Abdul Hamid, 27.
Officers in Malaysia have said they have been looking at the psychological background of the pilot from the start.
They have also examined their family life and connections as one line of inquiry into the flight's disappearance.
It has emerged that Shah was so passionate about flying he has is own flight simulator at home, and that Hamid once invited two women to spend an entire flight in the cockpit with him.
According to a local mosque leader, Hamid is a 'good boy, a good Muslim, humble and quiet'.
Hamid, the son of a high-ranking civil servant in Selangor state, joined Malaysia Airlines in 2007. With just 2,763 hours of flight experience he had only recently started co-piloting the sophisticated Boeing 777.
He had a short brush with fame when he was filmed recently for a CNN programme.
Hamid's superior, Shah, joined Malaysia Airlines in 1981 and has more than 18,000 flight hours.
Police have raided the luxury home of Fariq Abdul Hamid in Kuala Lumpur
His Facebook profile includes pictures of him flying remote-controlled aircraft, posting pictures of his collection which included a lightweight twin-engine helicopter and an amphibious aircraft.
Born in northern Penang state, the bald-headed captain and grandfather is also an enthusiastic handyman and proud home cook.
As part of what he called 'community service', he had posted several YouTube videos including how to make air conditioners more efficient to cut electricity bills, how to waterproof window panes and how to repair a refrigerator icemaker.
A Malaysian Airline stewardess who had flown with Shah several times said he was 'very nice, very friendly and safety-conscious'. She didn't want to be named because of company policy prohibiting employees from speaking to the media.
Neighbours of both men also praised their commitment to the community.
Hamid played futsal, a modified form of soccer popular in Southeast Asia, with neighborhood youngsters and paid for their sports shirts.
Neighbours said Shah was known for bringing food he cooked himself to community events or making sure his wife and children did when he couldn't attend
Shah was known for bringing food he cooked himself to community events or making sure his wife and children did when he couldn't attend.
A supporter of Malaysia's main opposition parties, he had volunteered to be a poll monitor in recent elections.
Yet both Hamid and Shah have quirks that reveal a more colorful side to their pilot personas.
Grabbing attention were pictures Shah posted online of the flight simulator he built for his home using three large computer monitors and other accessories.
Asked at a news conference whether it was unusual for pilots to have such equipment at home, Malaysia Airlines CEO Ahmad Jauhari Yahya said 'everyone is free to do his own hobby'.
Shah is certified by Malaysia's Department of Civil Aviation as a flight simulator examiner, according to Malaysia Airlines.
Agony: It has been more than a week since relatives of the missing passengers received any concrete evidence concerning their whereabouts
A handout map provided by the Indian Navy shows the revised search area for missing flight MH370 near the Andaman Nicobar islands, India
The Boeing 777's communication with the ground was severed just under one hour into the flight on March 8 from Kuala Lumpur to Beijing.
It has now been confirmed the plane turned back and crossed over the Malaysian peninsula after setting out on a northeastern path toward the Chinese capital.
The disabling of the Boeing 777's transponder and messaging system occurred around 12 minutes apart. Such a gap would be unlikely in the case of an in-flight catastrophe and gave authorities the clearest indication to date someone on-board was behind it.
The motive of the hijack is still not clear. No demands have been made and no groups have publicly claimed involvement in the disappearance.
Scott Shankland, an American Airlines pilot who spent several years as a co-pilot on Boeing 777s, said a captain would know how to disable radios and the plane's other tracking systems.
But a hijacker, even one trained to fly a plane, 'would probably be hunting and pecking quite a while' to find the correct way to switch off the equipment.
Some of the plane's data is transmitted automatically from equipment not located in the cockpit, making it even harder to avoid leaving electronic bread crumbs, he said.
Gone: The Malaysian Airways jet (not pictured) vanished on March 8 after communication was severed just one hour into a flight from Kuala Lumpur to Beijing
Search effort: Colonel Do Duc Minh (far left) Vietnam Air Force's 370 Division's Chief of Staff, points at a map as he speaks to reporters about search flights aimed at finding the missing Malaysia Airlines plane
John Hansman, an aeronautics professor at MIT who is familiar with the Boeing 777, said it would be possible for an intruder to turn off the transponders, but knowing how to shut down other systems in a bid to be stealthy would be more difficult.
Even if 9/11-style hijackers got that far, he said, they would be challenged to keep flying, make a successful landing, and hide the plane.
'If it was a hijacking, it was probably a hijacking gone bad,' he said.
Some experts have said that pilot suicide may be the most likely explanation for the disappearance, as was suspected in a SilkAir crash during a flight from Singapore to Jakarta in 1997 and an EgyptAir flight in 1999.
The already global search effort will now be expanded along the two large corridors outlined in his speech.
Indian navy ships supported by long-range surveillance planes and helicopters scoured Andaman Sea islands for a third day without any success in finding evidence of the missing Malaysia Airlines jet.
Nearly a dozen ships, patrol vessels, surveillance aircraft and helicopters have been deployed, but 'we have got nothing so far,' said VSR Murthy, an Indian coastguard official.
The Indian navy's coordinated search has so far covered more than 100,579 square miles in the Andaman Sea and the Bay of Bengal 'without any sighting or detection,' the Defence Ministry said.
The search has been expanded to the central and eastern sides of the Bay of Bengal, the ministry said.
Bangladesh also joined the search effort in the Bay of Bengal with two patrol aircraft and two frigates, said Mahbubul Haque Shakil, an aide of Bangladesh's prime minister, Sheikh Hasina.
Seeing no headway, Malaysian authorities suggested a new search area of 3,474 square miles to India along the Chennai coast in the Bay of Bengal, India's Defence Ministry said.
Developments, including the massive change in flightpath and subsequent radar detections, have ruled out the possibility of a huge mechanical failure.
It also means that extensive search efforts in the South China Sea have finished, with countries like Vietnam ending their involvement.
Isolated: A large-scale search operation was launched in the Anadaman Islands, but Indian Navy vessels have drawn a blank
No wreckage of the missing jet has been found, despite alleged sitings in various locations throughout the week.
The USS Kidd arrived in the Strait of Malacca late Friday afternoon. It uses a using a 'creeping-line' search method of following a pattern of equally spaced parallel lines in an effort to completely cover the area.
A P-8A Poseidon, the most advanced long range anti-submarine and anti-surface warfare aircraft in the world, will arrive Saturday. It has a nine-member crew and has advanced surveillance and reconnaissance capabilities, the department of defense said in a statement.
Malaysia has come under fire for what has been described as a 'pretty chaotic' search, with China saying the overall search effort has consequently been mired in confusion after a series of false alarms, rumors and contradictory statements.
Meanwhile, the hijacking news will renew focus on the two pilots at the helm of the missing Malaysia Airlines passenger jet.
The USS Kidd arrived in the Strait of Malacca late Friday afternoon and will be searching in the Andaman Sea, and into the Bay of Bengal
Expanded search: A Royal Malaysian Air Force Navigator captain Izam Fareq Hassan (right) talks with his team members onboard a Malaysian Air Force CN235 aircraft during a search and rescue (SAR) operation
Indian Navy officers during a search operation in the control room of a military aircraft. They were part of the team which scaled the Bay of Bengal and Andaman Islands
The only known blot on co-pilot Fariq's character appears to be the time 2011 when he invited two South African women into the cockpit when he and another officer flew a jet from Thailand to Malaysia.
In the days since the flight went missing, it has emerged that Shah was so passionate about flying he has is own flight simulator at home.
As the search continued for the missing Boeing 777, military radar suggested the plane was deliberately flown towards India's Andaman Islands.
Two sources familiar with the investigation said an unidentified aircraft - which investigators believe was flight MH370 - was plotted by military radar following a route between navigational waypoints.
Expanded search: Indonesian Search And Rescue personnel keep a lookout on a rescue ship heading to the Andaman sea
Wanting answers: Relatives of passengers of a missing Malaysia Airlines plane attend a conference with airline representatives at a hotel in Beijing, China on Saturday
Exhausted: Relatives of Chinese passengers aboard missing Malaysia Airlines flight MH370 rests in a room reserved for relatives awaiting news of the search for the plane
This indicates that it was either being flown by the pilots or someone with knowledge of those waypoints, the sources said.
The last plot on the military radar's tracking suggested the plane was flying towards India's Andaman Islands, a chain of isles between the Andaman Sea and the Bay of Bengal, they said.
Waypoints are geographic locations, worked out by calculating longitude and latitude, that help pilots navigate along established air corridors.
India recently began searching hundreds of uninhabited islands in the Andaman Sea, using heat-seeking devices.
Two Indian air force reconnaissance planes began flying over the islands as a precaution, after they and two naval ships scoured the seas surrounding the Andaman and Nicobar Islands, according to spokesman Col. Harmit Singh of India's Tri-Services Command on the territory.
The archipelago that stretches south of Myanmar contains 572 islands covering an area of 720 by 52 kilometers. Only 37 are inhabited, with the rest covered in dense forests.
Support: Thousands of people have written messages of support on a wall at a shopping mall in Kuala Lumpur, for passengers on board the missing Malaysia Airlines plane
Hope: Paper cranes are pasted on a message board for passengers aboard a missing Malaysia Airlines plane, at a shopping mall in Kuala Lumpur
A toy plane with messages of hope sits next to cards dedicated to people involved with the missing flight MH370 at Kuala Lumpur International Airport
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