The hearings come shortly before Congress is due to decide whether to ratify the trade agreement.

Trade between Vietnam and the US is still extraordinarily low

Vietnam has already described the hearing as a rude and "gross interference" in its internal affairs, saying deliberate attempts were being made to undermine rapprochement with the US.

The Communist Party newspaper Nhan Dan said on Tuesday that nobody was arrested in Vietnam because of their religious beliefs.

It said some Buddhists and followers of others religions had been detained - but only because they broke the law.

The hearings come hard on the heels of the worst unrest to hit Vietnam for years, involving mainly Protestant ethnic minority hill farmers in the central highlands.

Harassment

The BBC Hanoi correspondent says Vietnam currently recognises six religious groups, but organisations which lack official acceptance face sustained harassment.

Vietnam marked the 25th anniversary of the war this year

Last week, just ahead of the hearings, the communist authorities finally moved to recognize the country's largest Protestant church, the Evangelical Union of Vietnam.

The number two figure in the Unified Buddhist Church of Vietnam, Thich Quang Do, was nominated for last year's Nobel Peace Price by a group of US Congressman.

He was strip-searched after travelling to a remote area of central Vietnam.

Unrest

Last week, Vietnamese troops and riot police moved into the country's central highlands to quell protests by ethnic minority hill farmers.

Among the issues that sparked the protests was the government's repression of fringe Protestant churches, which have attracted many followers from ethnic minorities in recent years

The protesters key issue was the government turning the hill tribes' ancestral forests into the country's largest coffee-growing region, which has brought in lowland Vietnamese.