The missing Malaysia Airlines jetliner had its communication systems disabled and was deliberately flown off course, Malaysian Prime Minister Najib Razak said Saturday.
At a press conference, Razak said there is a "high degree of certainty" that the data reporting system of Malaysia Airlines flight MH370 was disabled just before it reached the east coast of Malaysia. After which, he said the plane flew in a westerly direction back over the Malaysian peninsula before turning northwest until the point at which it left military primary radar coverage.
"These movements are consistent with the deliberate action by someone on the plane," Razak said.
As such, Malaysian authorities have refocused the investigation into the crew and passengers on board.
Despite media reports that the plane - carrying 227 passengers and 12 crew members from Kuala Lumpur to Beijing - was hijacked, he said authorities are still investigating all possibilities as to what caused the flight to deviate from its original flight path.
(Read more: Missing MH370:Timeline of latest developments)
The last confirmed communication between the plane and a satellite was at 8:11a.m. Malaysian time, he said, more than six hours after it vanished from civilian radar around 1:30 a.m. on March 8 without a distress call.
"The investigation team is making further calculations – which will indicate how far the aircraft may have flown after the last point of contact. Due to the type of satellite data, we are unable to confirm the precise location of the plane when it last made contact with a satellite," he said.
However, Razak said the investigators believe the aircraft is likely to be in one of two "corridors": north from the border of Kazakhstan and Turkmenistan through to northern Thailand, or south from Indonesia to the southern Indian Ocean.
"Clearly the search for MH370 has entered a new phase," Razak said.
Relatives digest new developments
Many families of the Chinese passengers aboard MH370 were surprised by the latest revelations announced by the Malaysian Prime Minister.
Hundreds of families were watching the press conference on state TV live from a conference room in a Beijing hotel where they have been camped out for the past week.
Malaysian caregivers were on standby to assist the families, while the Malaysian ambassador to China was also present.
At one point, there was a collective gasp in the room when the relatives heard the Prime Minister say that the last satellite communication with the flight was at 8:11 local time – several hours longer than previously thought.
Relatives told CNBC that the comment raised hopes that the passengers may still be alive. However, most families are still frustrated with the waiting.
Wang Le, a website editor whose mother was on board the flight, said: "Nothing new, we could have found this information online. [I] don't understand why they called this briefing."
When asked whether the newly revealed time of last contact gave him hope, he said, "Of course I hope the plane has landed safely but frankly I have not been following the news in the last few days because whenever I think of the missing plane I feel sad and think of my mom."
"I just hope there is conclusion to all of this soon," he added.
China's foreign ministry said on Saturday it was demanding that Malaysia keep providing more thorough and accurate information about the flight.