Ammon News - (AFP) - Malaysia's leader on Saturday said communications aboard a missing jet were switched off and its course deliberately changed by someone on board before the aircraft disappeared a week ago, but stopped short of saying it had been hijacked.

Final satellite communication with the Boeing 777 flying from Kuala Lumpur to Beijing came more than six-and-a-half hours after it vanished from civilian radar at 1:30am on March 8, Prime Minister Najib Razak told a nationally televised press conference.

The movement of the plane in the interim period, during which it changed direction and passed back over the Malaysian peninsula towards the Indian Ocean, was "consistent with deliberate action by someone on the plane," Najib said.

"Despite media reports that the plane was hijacked, I wish to be very clear: we are still investigating all possibilities as to what caused MH370 to deviate from its original flight path," he added.

Najib said his announcement was based on new information from satellite contact with the plane and military radar data.

The combined data suggested "with a high degree of certainty" that the plane's two automated communications systems Aircraft Communications Addressing and Reporting System (ACARS) and its transponder were "switched off" one after the other before it reached the point over the South China Sea where it dropped out of civilian radar contact.

It then turned back and flew in a westerly direction back over peninsular Malaysia before turning northwest.

The last confirmed communication between the plane and satellite was at 8:11 am, Najib said, adding that investigators were calculating how far the aircraft may have flown afterwards.

So far, experts had located the last point of communication as being inside one of two large geographical corridors: a northern corridor stretching from the border of Kazakhstan and Turkmenistan to northern Thailand, and a southern corridor stretching from Indonesia to the southern Indian ocean.

"This new satellite information has a significant impact on the nature and scope of the search operation," the prime minister said.

"We are ending our operations in the South China Sea and reassessing the redeployment of our assets. We are working with the relevant countries to request all information relevant to the search, including radar data," he added.