"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.
They said they plan to stay through the Chinese Lunar New Year holiday, which begins tomorrow, 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.
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.
The group held a protest at Malaysia Airlines' headquarters last weekend.