Grieving Chinese relatives of MH370 passengers blasted Malaysia Airlines on Friday, detailing a long list of complaints and traumas they said were suffered as a result of the flight's mysterious disappearance 11 months ago.

The 21 family members arrived in Malaysia last week from China to demand authorities cancel a declaration that the plane's 239 passengers and crew were presumed dead, and voiced discontent over the airline's responses to questions they submitted on a litany of issues.

At a news conference in Kuala Lumpur, they showed journalists photos of Chinese passengers' relatives who suffered emotional and physical trauma, including one elderly man whom they claimed had a stroke after hearing of Malaysia's declaration about the passengers.

"We are extremely dissatisfied with the replies from Malaysia Airlines," said Jiang Hui, whose mother was on the ill-fated flight.

"The answers were contradictory and not within the scope of the questions asked."

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

Xu Jinghong, 43, whose mother was also on MH370, told AFP the Malaysia Airlines support centre in Beijing was not helpful and expressed fears search operations might be called off.

"We think the plane can be found. I don't think they are searching at the right area," she said.

"I don't think it's in the sea."

Malaysian authorities issued the declaration on the plane last month, drawing howls of protest from next of kin in Malaysia and China, many of whom have sharply criticised the airline's and Malaysian government's handling of the tragedy.

- Search efforts -

Authorities say it allows families to move on and seek compensation, but stressed that search efforts would go on for now.

Malaysia Airlines could not immediately be reached for comment Friday.

It defended itself against the Chinese relatives' criticisms in a statement to AFP on Wednesday, saying that since the declaration it had deployed additional resources at a family support centre in Kuala Lumpur.

It also reiterated a standing offer of a $50,000 advance payment to next of kin that does not waive rights to future compensation claims, and said it had gone "in many instances, beyond international best practices" in its MH370 response.

"It is hoped that all interested parties mutually respect and support each other in this very difficult time," the statement said.

The Chinese relatives also criticised Boeing, saying the US manufacturer of the plane refused to answer their queries on whether any "product design and structure" issues may be responsible for the mystery.

MH370 vanished on a routine red-eye flight from Kuala Lumpur to Beijing on March 8 in one of the greatest mysteries in aviation history.

Malaysia 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 are yet to release any findings from their various investigations into the incident.

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