The defendants, who include Catholics, bloggers and students, appeared in a provincial court in Nghe An, about 300 kilometres south of Hanoi, a court clerk told AFP, declining to provide further details.

They are accused of being members of the Viet Tan group, which is labelled by Hanoi as a terrorist organisation.

If convicted the 14 - who are aged between 24 and 55 - could in theory face the death sentence, although the Communist regime has never executed anyone for anti-state activity.

The authoritarian country's state-controlled media made no mention of the trial, which overseas activists said was one of the largest of its kind.

Charges of spreading anti-state propaganda and attempting to overthrow the regime are routinely laid against dissidents in a country where the Communist Party forbids political debate.

The defendants are part of a group of 17 people who have appealed to the UN's working group on arbitrary detentions to intervene on their behalf. The three others were sentenced in May for spreading anti-state propaganda.

The detainees have suffered various violations of human rights according to Stanford Law School lecturer Allen Weiner who is assisting with their petition to the UN.

"Most of the petitioners have been jailed for an extended period of time without meaningful judicial process," he said in a statement.

"Those petitioners who have been brought to court have been convicted after perfunctory hearings lasting only a few hours," he added.

Activists on Tuesday posted photos online showing hundreds of police surrounding the courtroom in Nghe An, saying that several people who had turned up to support the detainees had been harassed and detained.

Rights group say dozens of peaceful political activists have been sentenced to long prison terms since Vietnam, a one-party state, launched a fresh crackdown on free expression in late 2009.

Australian Associated Press - January 8, 2013