Seven Vietnamese dissidents, including three US citizens, were found guilty of plotting against the Vietnamese Government in Ho Cho Minh City today.

At the one-day trial, the dissidents were sentenced to 15 months imprisonment for "terrorist activities", including planning bomb attacks on Vietnamese government buildings and distributing leaflets that called for the overthrow of communist rule.

Two tables near the entrance of the Ho Chi Minh City People’s Court were covered in radio equipment and transmitters that the group was allegedly planning to use to jam the airwaves of pro-government radio stations and broadcast their own message of uprising.

The seven have already served most of their sentences because they have been behind bars since their arrest last September. They are expected to be released in December. The three American citizens, including the prominent campaigner, Nguyen Thuong Cuc, will be deported within 10 days of their release.

The case has proved a diplomatic embarrassment to both America and Vietnam ahead of next week's meeting of the Asia-Pacific Economic Cooperation (Apec) forum in Hanoi, when both President Bush and the US Secretary of State, Condoleezza Rice, are scheduled to visit the country.

Mel Martinez, a Republican Senator from Florida, has lobbied the Bush Administration on behalf of Nguyen Thuong Cuc, the best known dissident and a resident of Orlando, Florida, and reportedly threatened to disrupt a trade deal between the US and Vietnam unless the case was brought swiftly to court.

Ms Cuc, better known in the US as Thuong Nguyen Foshee, has lived in Florida for decades after fleeing Vietnam in the 1960s. She has close ties with the Republican Party and her family describe her as a pro-democracy activist rather than a rebel against Vietnam's one-party government.

But she was arrested last year, along with fellow American residents, Huynh Bich "Linda" Lien, 51, and Le Van "Phu" Binh, 30, because of her ties to another US-based dissident group, the Government of Free Vietnam", which is listed as a terrorist organisation in Vietnam.

The Government of Free Vietnam, which is based in California, is run by Nguyen Huu "Tony" Chanh, a former soldier in the South Vietnamese army who has campaigned against communist rule in the country since the Vietnam War.

Wanted in Vietnam for allegedly plotting to bomb Vietnamese embassies, he was arrested in South Korea in April but was allowed to return to the US after the countries failed to agree his extradition.

Speaking in court today, Ms Cuc and her fellow defendants denied terrorism but admitted breaking Vietnamese laws. "I very much regret my participation in Nguyen Huu Chanh’s organisation," she said. "I had lived outside of my country for nearly 40 years so I didn’t understand my country and the laws in Vietnam".

Sentencing the group to 15 months in prison — a light sentence considering the seriousness of the charges — Judge Vu Phi Long told the court: "This is a very dangerous crime that put people’s life in danger and is condemned by the international community."

Vietnamese nationals Tran Dat Phuong, 65; brothers Ho Van Giau, 59, and Ho Van Hien, 38, all of southern An Giang province; and Cao Tri, 35, a US resident, were also sentenced for their part in the alleged conspiracy. They were ordered to remain under house arrest for three years after their release next month.

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