Chinese relatives of MH370 passengers gathered outside the Malaysian prime minister's office Wednesday to demand his government rescind its declaration that all on board the plane were presumed dead.

"We want an explanation from (Prime Minister Najib Razak). And we want him to cancel the declaration that the incident was an accident," said Kelly Wen, a Chinese national whose husband was on the Malaysia Airlines flight.

Malaysian authorities last month declared the plane's unexplained disappearance an "accident" under global aviation conventions, saying for the first time that all 239 passengers and crew were presumed dead.

That set off howls of protest from next of kin in Malaysia and China, many of whom have sharply criticised the airline and Malaysian government over the plane's disappearance.

A group of 21 relatives from China, where criticism from families has been especially intense, came to Malaysia last week to demand the declaration be cancelled and press for information on the plane's fate.

They said they plan to stay through the Chinese Lunar New Year holiday, which begins on Thursday, and until they get answers.

"We want to tell Prime Minister Najib that we want our families back for the Spring Festival," said Wen, using the Chinese term for the holiday.

"They have said our relatives are dead but have given no proof. This is unacceptable."

The next of kin then presented a representative from the prime minister's office with Chinese calligraphy scrolls calling for their relatives' return.

They later held an emotional Lunar New Year prayer session at a nearby square, with some wailing loudly and calling out "Come home!"

Two-thirds of the plane's passengers were Chinese.

The plane vanished en route from Kuala Lumpur to Beijing last March 8 in one of history's great aviation mysteries.

The Chinese next of kin said the onset of their culture's most important holiday had worsened their pain and suffering, as the festival is normally a joyous time of family gatherings.

"Bringing our families together for Spring Festival is the most important thing to Chinese people," said Wang Rongxuan, 60, whose son Hou Bo, 37, was on the plane.

"Now, how can we celebrate? I have been dreading this -- passing the holiday without our son."

The group held a protest at Malaysia Airlines' headquarters last weekend.

Malaysia's government says satellite data indicates the plane inexplicably detoured to the remote southern Indian Ocean, which they suspect was due to "deliberate" action onboard.

But no evidence has turned up despite an intensive search there, and Malaysian authorities still have released no findings from their various investigations into what happened.

Some relatives accuse Malaysia and the airline of a bungled response to the disaster and possible cover-up, charges that are denied.

Malaysian authorities say last month's declaration allows families to move on and seek compensation.

But many relatives angrily reject the suggestion, saying they fear the move is an attempt by Malaysia to wash its hands of MH370 and leave it unsolved.