The arrests were the latest in a string of crackdowns by the government on local dissidents and exiled groups, including two that it designated as terrorist groups.

The official police newspaper Cong An Nhan Dan reported on Saturday that "Trieu Dai Viet", or Viet Dynasty, was behind a bombing of a police station in Ho Chi Minh City in June.

The incident, in which two small explosive devices were detonated, injured three people. Police said in July that they had arrested seven people in relation to the case.

Canada-based Trieu Dai Viet, with a motto to "fire all", "kill all", "destroy all", "steal all", also planned to bomb houses of some local provincial officials but were stopped by police, the newspaper reported.

The details could not be independently confirmed by Reuters and no comment was available from the group.

Trieu Dai Viet was founded by former key members of the California-based Provisional National Government of Vietnam, which is loyal to the now defunct state of South Vietnam, who broke away due to a conflict of ideas, the newspaper's website said.

The Provisional National Government of Vietnam was listed by Vietnam as a terrorist organisation in January.

Ngo Van Hoang Hung, founder of Trieu Dai Viet, was given a life sentence in Vietnam in 1979 but fled to Canada and never returned to Vietnam. The group spreads their message through Facebook and Youtube, the report added.

The arrest came just before Vietnam celebrated its National Day holiday on Sept. 2 and after Vietnam ordered police and military forces in the capital Hanoi to prevent big gatherings or protests.

Earlier this week, police arrested a man accused of being a member of the Viet Tan group, which Vietnam also regards as a terrorist organisation, on suspicion of planning attacks after he entered Vietnam from Cambodia with a large number of weapons.

Viet Tan, which describes itself as an "unsanctioned pro-democracy party", rejected the allegations and said the police are trying to scare people not to support pro-democracy organisations by falsely accusing them of smuggling weapons.