The incident took place in Bac Giang province northeast of Hanoi on Sunday, said the official from the provincial People's Committee, the local government.

"Thousands of people were in front of the People's Committee... to ask for the truth" about the death of the man who was held for a traffic violation, said the official, who declined to be named.

He said they had brought the young man's coffin with them.

"Mobile police had to use tear gas to disperse the crowd," the official said. Six people who resisted the officers were detained for questioning but later released, he added.

"The situation is calm now," he said.

Vietnam News, which is published by the official Vietnam News Agency, reported on the death but made no mention of tear gas or the large crowd of protesters.

It said Nguyen Van Khuong, 21, was found to be in "abnormal health" while sitting in a chair at a traffic police station after he was detained. He was sent to hospital but was dead on arrival, Vietnam News said.

"The main reason why people get so upset by these kind of actions is they view most traffic police as 100 percent corrupt," said a foreign diplomat, who asked not to be named.

He said the dead man's family went to the local government in search of justice.

"They took the coffin to the People's Committee and they tried to push it in," said the diplomat.

He said he understood that the protesters "sort of broke in to the main People's Committee area".

Vietnam News said the results of an autopsy have not been released.

It quoted Bui Van Hai, deputy chairman of the People's Committee, as saying the case would be dealt with honestly and that any violations would be punished.

A police investigator told AFP the matter had been settled.

Agence France Presse - July 28, 2010