Update | New search focus after satellite confirms Malaysia Airlines flight did change course after losing radar contact

Malaysian Prime Minister Najib Razak says investigators now know that the missing Malaysian airliner’s communications were deliberately disabled and that it turned back from its flight to Beijing and flew across Malaysia.

Exactly a week to the day since flight MH370 went missing, he told a packed press conference that the plane's last satellite contact indicates two possible flight corridors which are now the focus of the search - Kazakhstan and Turkmenistan to Northern Thailand, and the southern corridor of Indonesia to the southern Indian Ocean.

He confirmed that the plane's transponders - which send back information to civilian radar regarding performance, location and altitude - were deliberately switched off, but denied that investigators had concluded hijacking as the reason why the jet vanished. However, he did say the aircraft's disappearance was a result of “deliberate action” by someone on board.

Najib was responding to earlier claims on Saturday from a Malaysian government official that investigators had concluded that one of the pilots or someone else with flying experience hijacked the missing Malaysia Airlines jet.

The official, who is involved in the investigation and spoke to Associated Press on condition of anonymity because he was not authorized to brief the media, had said that hijacking was no longer a theory. “It is conclusive.”

But Prime Minister Najib would only go so far as to say that all possibilities were being investigated, before adding: “In view of this latest development, the Malaysian authorities have refocused their investigation into the crew and passengers on board.”

He said that after the transponders were disabled, the aircraft - carrying 12 crew and 227 passengers - turned back and flew in a westerly direction before turning north west.