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.
Using a projector at a news conference held at a Kuala Lumpur hotel, they showed journalists photos of relatives of the passengers suffering emotional and physical trauma in China, including one elderly man whom they claimed suffered 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."
Xu Jinghong, 43, whose mother was also on MH370, said 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."
The declaration that MH370's disappearance was an "accident" and that the crew and passengers -- two-thirds of whom were Chinese -- were presumed dead set off howls of protest from next of kin in Malaysia and China, many of whom have sharply criticised the airline and Malaysian government.
Authorities say the declaration allows families to move on and seek compensation.
Boeing was also criticised, as the group of relatives claimed the US plane manufacturer refused to answer their queries on "product design and structure."
MH370 vanished while on a routine 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 have still yet to release any findings from their various investigations into the incident.
Some relatives accuse Kuala Lumpur and the airline of a bungled response to the disaster and possible cover-up, charges that have been denied.

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