BEIJING (AFP) - China spearheaded fresh criticism on Sunday of Malaysia's handling of a missing airliner drama, saying it "squandered" precious time and resources by releasing dramatic information on the plane's fate a full week after it vanished.

Prime Minister Najib Razak revealed a day earlier that an investigation indicates Malaysia Airlines flight MH370 was deliberately diverted and flew for several hours after leaving its intended flight path, though he stopped short of saying it was hijacked.

The startling revelation after a week of confusion and competing theories, prompted questions over how long Malaysian authorities had been privy to the new data, and whether they had missed an opportunity to intercept the diverted plane.

"It is undeniable that the disclosure of such vital information is painfully belated," a scathing editorial by China's state-run Xinhua news agency said, noting the "excruciating" seven days it entailed for relatives of the missing.

It suggested Malaysian officials were guilty of an "intolerable" dereliction of duty.

Two-thirds of the passengers on board the flight from Kuala Lumpur to Beijing were Chinese.

There was particular anger and frustration that Malaysia had taken so long to cancel search operations in the South China Sea if it already knew the plane had doubled back and flown towards the Indian Ocean.

"And due to the absence - or at least lack - of timely authoritative information, massive efforts have been squandered, and numerous rumours have been spawned," the editorial said.

Mr Najib revealed on Saturday that the Boeing 777's communications systems had been manually switched off - one after the other - before the jet veered westward.

He cited satellite and military radar data that made investigators believe it had been deliberately diverted by someone on board and flown on for hours - either south into the Indian Ocean or north towards South and Central Asia.

"As the leader of the international search and rescue mission, Malaysia bears inescapable responsibility," it added.

There was similar outrage among users of the micro-blogging network Weibo - China's version of Twitter.

"The Malaysian government's behaviour in this affair can be summed up in one word: 'deceptive'," said one typical comment.

The now week-long search for the Boeing 777 initially focused on waters in the South China Sea between Malaysia and Vietnam, where the plane disappeared from primary radar on March 8.

Much of the data confirmed by Mr Najib had already been leaked in the US media, but it was only on Saturday that he announced the end of search operations in the South China Sea.

The prime minister insisted that Malaysia had not allowed national security concerns to prevent the "real time" sharing of confidential information with other authorities.

"We understand the desperate need for information ... but we have a responsibility to the investigation and the families to only release information that has been corroborated," he said.

Malaysia Airlines also issued a statement defending the delay between acquisition of the satellite and radar data and Mr Najib's statement.

"It was critical that the raw satellite signals were verified and analysed ... so that their significance could be properly understood.

"This naturally took some time, during which we were unable to publicly confirm their existence," the statement said, adding that validating new information before releasing it would remain "paramount".

But security and aviation experts continued to question why so many resources were deployed in searching the South China Sea for so long, and how the Malaysian military had failed to identify the plane as it backtracked over the peninsula.

"It is an astonishing failure of security," said Ajaj Sahni, executive director of India's Institute for Conflict Management in New Delhi.

"And it seems an astonishing failure of technology in every aspect that something like this could happen."

Mr Terence Fan, an aviation expert at the Singapore Management University, said Malaysia's crisis management was flawed and had tested public confidence.

"Why did they need days to 'corroborate' from their own radar images that the airplane could have turned west?" Mr Fan said.

"Couldn't they have known from day one that the different communications systems on the aircraft were turned off at different times?" he added.