CNRP leader Sam Rainsy plans to file a lawsuit against Prime Minister Hun Sen and National Assembly President Heng Samrin for crimes allegedly committed during the execution of the controversial K5 Plan, he said in a Facebook post yesterday.

Last week, the opposition leader had mocked the two for suing him over “petty” issues, while ignoring his “crimes against humanity” accusations.

The K5 Plan was a strategy to prevent Khmer Rouge forces from freely moving back and forth from Thailand by seeding the border with thousands of landmines, mainly between 1984 and 1987.

Historians estimate that as many as 380,000 Cambodians were forcibly conscripted, and thousands are thought to have died from malaria and landmines. Hun Sen became prime minister in 1985.

Rainsy, who could not be reached yesterday, said that he was “building the case for the international court to arrest Hun Sen and Heng Samrin and to convict [them] according to the international law”.

He did not specify which court he would file the lawsuit with, though international lawyers sympathetic to the opposition are currently pushing a case against the government at the International Criminal Court.

But CPP spokesman Sok Eysan yesterday dismissed any such attempt as Rainsy’s last political move, saying an amendment to the law on political parties recently proposed by the premier would soon see him expelled from party politics based on past convictions.