The comment came as the wife of another dissident - a former Communist Party official - told AFP that he was the latest to be arrested.

Vi Duc Hoi, 54, was detained Wednesday at the family home in northern Lang Son province bordering China, said his wife, Hoang Thi Tuoi.

His arrest came on the same day that communist Vietnam, after a trial lasting less than a day, jailed three labour activists who reportedly organised strikes and gave out "reactionary" leaflets.

One was jailed for nine years while the other two received seven-year sentences, said a court official in the southern Mekong Delta.

In a statement, the US embassy said it was concerned by the convictions and also troubled by the arrest of two bloggers and re-arrest of a third.

Those actions, together with the trial on Wednesday of several Catholic parishioners, "contradict Vietnam's own commitment to internationally accepted standards of human rights. We urge the government of Vietnam to release these individuals," the embassy said.

It said three of the accused parishioners were denied their right to legal representation under Vietnamese law.

Official media reported that, after a trial in the central city of Danang on Wednesday, the villagers were convicted with the most severe sentence of one year in jail. Another person was jailed for nine months while the rest had their sentences suspended, the reports said, adding that all of the accused were involved in a public disturbance.

Residents said in May that the villagers were arrested after a clash with a large group of police over a cemetery in Con Dau Catholic parish, near Danang.

Three US Congressmen alleged the villagers had been tortured, and asked top Vietnamese leaders to intervene and consider granting their unconditional and immediate release.

Other US lawmakers on Wednesday called on Clinton to raise human rights with Vietnam during her visit to the country beginning Friday.

The latest appeal was led in part by Representative Loretta Sanchez.

She and three other members of Congress asked Clinton to "raise specific cases and demand actual progress" when she meets Vietnamese leaders on the sidelines of a summit between leaders of the Association of Southeast Asian Nations (ASEAN) and other countries in the region.

British-based global rights watchdog Amnesty International said Vietnam must "stop this needless crackdown on government critics and peaceful activists".

Vietnam's Ministry of Foreign Affairs said the arrests and trials just before the ASEAN meetings were conducted to enforce the law.

"The practice of law to ensure social order and discipline is a normal act of every nation," a ministry spokeswoman told AFP.

US-based Human Rights Watch called for Clinton, during her visit, to speak out against an "intensifying campaign of harassment, arrest, beatings in custody, unfair trials, and long prison terms" against peaceful bloggers, community activists and others.

Watchdogs say there have been a series of rights violations against politically-oriented bloggers in Vietnam.

The blogs typically touch on official corruption, a controversial bauxite mining development, and relations with China, said Phil Robertson, the deputy director of Human Rights Watch's Asia division.

Tuoi, wife of the latest detainee, said that, as far as she knew, her husband had written articles "about general anti-corruption issues".

She said he told her that he was arrested on a charge of propaganda against the state, which carries a maximum 20-years prison term.

By Ian Timberlake - Agence France Presse