Hanoi: Vietnamese prosecutors have accused 18 members of a little-known "reactionary" group of plotting to overthrow the communist government, official media reported Thursday.
Police said they arrested the leader and 17 other members in February after a series of raids on the group's secret rural command centre in Phu Yen province. They have been in detention ever since.
Prosecutors initially said the 18 men were being investigated for "abusing freedom and democratic rights to violate state interests", a lesser charge that carries a maximum of seven years in prison.
But group leader Phan Van Thu and the others have since admitted to a charge of aiming to "overthrow the regime", the Phu Yen local government newspaper reported on its website, quoting an official.
The charge in theory carries the death penalty, although Vietnam has never executed people for political crimes.
"Evidence and documents confiscated showed that the reactionary group had a plot to topple the people's administration," the report said.
Rights campaigners say the accusation that a group is conspiring to overthrow the state is regularly used to silence dissidents in authoritarian Vietnam, where the communist party limits political debate.
Police said at the time of the arrests that the organisation, called Hoi Dong Cong Luat Cong An Bia Son in Vietnamese, operated "non-violently" but aimed to overthrow the current administration.
The group, which police say was set up by Thu in 1975 but was little known to the public, is said to have a number of associations in cities and provinces across Vietnam and more than 300 members, including Vietnamese abroad.
No overseas Vietnamese dissident group has claimed to be linked to the group.
During the raids, police said they confiscated hundreds of documents on the operational rules of the group along with laptops, cameras and communication equipment, and tens of thousands in US dollars and Vietnam's dong currency.
The group's name translates as Council for the Laws and Public Affairs of Bia Son, but there is scant information about its aims beyond the Vietnamese police account. Bia Son is a mountain in Phu Yen province.