Civil aviation chief Azharuddin Abdul Rahman said the search for the jet would continue and "remains a priority". The Boeing 777 disappeared on March 8, 2014, while flying from Kuala Lumpur to Beijing with 239 people on board.

The plane is believed to have crashed in the southern Indian Ocean, off the coast of western Australia. No confirmed debris has ever been found.

The declaration will help facilitate financial claims by families, and Malaysia Airlines is ready to proceed with the compensation process, Azharuddin said.

"After 327 days, and based on all available data as well as circumstances ... survivability in the defined area is highly unlikely. It is therefore with the heaviest heart and deepest sorrow that we officially declare Malaysia Airlines Flight MH370 an accident," he said in a pre-recorded statement broadcast on Malaysian television.

unanimous decision

Transport Minister Liow Tiong Lai said the governments of Malaysia, China and Australia had agreed on the announcement, which was intended to "enable the families to move forward".

However, in China, where most of the passengers came from, some family members refused to accept the official position that the plane crashed.

"There's nothing new. The Malaysian authorities have been covering up the truth from the get-go, and they have no credibility to speak of. We are not accepting the conclusion," said Wen Wancheng, whose son, Wen Yongsheng, was on the plane.

"Because you have no evidence at all. How can you come to such a conclusion?" said Wang Chunjiang, who lost his brother, Wang Chunyong.

"Chinese New Year is coming up. Why did you choose now to make the announcement?"

Li Jingxin, the brother of Li Zhixin, a labourer who was returning to China on the flight, said the family would not accept any compensation from the airline for now.

"They have found nothing. With nothing found, how can they make any announcement?" Li said.

no expense spared

Azharuddin said that Malaysia, China and Australia had spared no expense and resources in their search for the plane, but were still unable to locate it.

The hunt resumed in October, after a four-month hiatus, with more sophisticated sonar equipment. The Australian coordinators of the search have said the current underwater phase could take another year, and there is still no guarantee of success.

Azharuddin said the Convention on International Civil Aviation, commonly referred to as the 'Chicago Convention', states that the definition of the term "accident" includes "the aircraft is missing".

He said investigations by the safety team and Malaysian police were ongoing, but both were limited by the lack of physical evidence, particularly the flight recorders.

"At this juncture, there is no evidence to substantiate any speculations as to the cause of the accident," he said. An interim report detailing the progress of the investigation is to be released on March 7.

Jiang Hui (left) and Dai Shuqin, relatives of passengers on board the Malaysia Airlines Flight 370 that went missing on March 8,