"We want the truth!" "Give our loved ones back!" shouted the protesters. A few threw water bottles over the gate onto embassy grounds. Some were seen being shoved about by plainclothes security officials, but no serious clashes appeared to have broken out.

One female family member in a white t-shirt fainted and fell on the ground, and was carried away on a stretcher.

Earlier on Tuesday morning, several hundred family members of the doomed flight's passengers had stormed out of the Lido Hotel they were staying at and travelled to the Malaysian embassy in downtown Beijing by bus. Some family members told reporters later that they had hired the buses themselves. 

There was more shoving and shouting when protesters tried to take reporters with them across the police lines, but the policemen stopped all the reporters and only allowed some family members to pass.

The crowds calmed down after an embassy official came out and accepted a letter of protest from family members, witnesses told Post reporters who were stopped at the police line. The protesters began to disperse in the early afternoon as passengers' family members boarded several buses and left for the hotel. Other protesters left on their own without incident.

Policemen also removed roadblocks near the embassy after protesters left, but much of the police, paramilitary and plainclothes security presence remained outside the embassy compound as of early afternoon.

Many distraught family members have accused the airline and the Malaysian government of repeatedly lying to and misleading them about the fate and whereabouts of their loved ones on board the missing flight.

There were screams of disbelief and uncontrollable sobbing when the Malaysian government informed family members late Monday evening that they had concluded the plane had crashed in the Indian Ocean, and nobody on board survived. 

"I can't take this," shouted a middle-aged woman who had to be supported by two men in the Beijing hotel where relatives were summoned ahead of the announcement that the jet was lost.

"Why is the Malaysian government doing this to us?" cried a man. Paramedics were on hand to help those who simply could not cope with the terrible news.

Reporters were kept out of the room, as they were at a Kuala Lumpur hotel where a similar family meeting was held.

Watch: MH370 relatives in China distraught as hope extinguished

But some family members spoke publicly when they left, some hurling abuse at the Malaysian government.

A woman, held by family on both sides, begged journalists for help. "Reporters, help us say something to the governments," she cried.

"Don't they have children themselves? Are their children all dead? Why are they doing this? I need the governments to speak to us direct. It's not right that they announce this now."

Some relatives in Beijing lashed out as they left their meeting with the Malaysian flag carrier, with one man throwing punches and kicks at assembled media.

One woman left the room shouting “Murderers! Murderers” and crying uncontrollably as she was held by two other family members, while another swiped at cameramen with her handbag, shouting “Get away!”

At about 2am a group of around 30 relatives came out of the room to meet waiting reporters.

“The Malaysian government, Malaysian Airlines and the Malaysian armed forces are the real murderers who have killed our loved ones,” a man said, appearing to read from a prepared statement on a laptop on behalf of the group.

“The relatives of the passengers launch the strongest protest and condemnation” against them, he added.

The man also said the relatives would use “all possible means” to protest.

In a statement from the Chinese Family Committee, the families criticised the Malaysian government over its handling of the investigation into the fate of MH370.

"From March 8 when they announced that MH370 lost contact to today, 18 days have passed during which the Malaysian government and military constantly tried to delay, deceive the passengers' families and cheat the whole world," the statement said.

"This shameless behaviour not only fooled and hurt the families of the 154 passengers but also misguided and delayed rescue actions, wasting a large quantity of human resources and materials and lost valuable time for the rescue effort.

"If the 154 passengers did lose their lives, Malaysia Airlines, the Malaysian government and military are the real executioners who killed them. We the families of those on board submit our strongest protest against them.

"We will take every possible means to pursue the unforgivable crimes and responsibility of all three."

Family members have been among the most distrusting of Kuala Lumpur from the outset. Statements have often been corrected or retracted.

And last night's announcement by Malaysian Prime Minister Najib Razak that analysis from UK specialists had confirmed that the plane's last known location was in the middle of the Indian Ocean, far from any possible landing site, did little to quell their anger and suspicion.

Among the increasingly suspicious relatives was Zheng Xi, a thirtysomething woman from Nanjing who spoke to the by phone. "Malaysia knew what happened to the plane," Zheng, who had two relatives on board, said. "They knew all along but they wanted to act like they didn't. They wanted to divert people's attention and get as many countries involved as possible and then tell people that the plane was lost in the world's most remote location."

Even if she has given up on ever seeing her relatives alive, she said she felt no closure because the bodies have not been recovered.

"We will not stop searching, we will go to the Premier of China if we have to. We will find them," she said.