Phay Siphan, secretary of state and spokesman of the Council of Ministers, told Kyodo News that the lawsuit was filed at the Phnom Penh Municipal Court against Sam Rainsy, who was sentenced Jan. 27 in absentia to two years in prison for having led villagers to uproot border markers on the border with Vietnam in October last year.

Kim Sour Phirith, spokesman of the Sam Rainy Party, called the lawsuit part of the strategy of the ruling Cambodian People's party to weaken and silence the opposition party, especially its leader who dares to criticize the wrongdoings of the government.

He said as long as the politically biased Cambodian judicial system is involved, no "justice will be rendered" to Sam Rainsy.

Prime Minister Hun Sen on Wednesday called Sam Rainsy a traitor and said he will not be allowed to run in the 2013 general election.

Hun Sen said while Cambodia is in conflict with Thailand over a disputed border area, Sam Rainsy has attempted to divert the nation's attention to an alleged border issue with Vietnam.

Such action could create a schism in the country's armed forces and cannot be "tolerated."

Sam Rainsy, who lives in exile in France, has defended his action at the border with Vietnam by saying wooden poles had been planted in the rice fields 200-300 meters inside Cambodian territory by Vietnamese authorities and "complacent" Cambodian counterparts.

He said villagers uprooted them "to symbolically show their refusal to give up ancestral rice fields they had been cultivating since 1979 and to be deprived of their livelihoods."

The Cambodian and the Vietnamese governments have rejected Sam Rainsy's accusation as groundless.