PHNOM PENH, Cambodia (AP) — Cambodia's opposition party leader on Wednesday accused the government of restoring single-party rule following physical attacks on some opposition lawmakers and legal moves to purge others from the legislature.

Cambodia National Rescue Party leader Sam Rainsy made the accusations in a posting on his Facebook page, accusing the ruling Cambodian People's Party of derailing democracy established by a 1991 U.N.-led peace agreement ending years of civil war.

A court last week ordered Rainsy's arrest on an old defamation conviction that many believed had been lifted by a 2013 pardon. The ruling party-dominated National Assembly stripped Rainsy of his lawmaker's status and parliamentary immunity on Monday, prompting him to delay his return from an overseas trip.

Prime Minister Hun Sen has in recent months put pressure on the opposition party, with which he had reached a political truce in 2014 to end a boycott of Parliament. The opposition had accused Hun Sen's party of stealing the 2013 general election.

Rainsy's party has been making political inroads this year by highlighting what it says is the loss of national territory to neighboring Vietnam, Cambodia's traditional enemy. The government responded by pursuing cases in court against its opponents, with harsh sentences handed down in questionable proceedings.

Late last month, two opposition lawmakers were savagely beaten by members of a pro-government mob. Shortly afterward, opposition party deputy leader Kem Sokha was removed from his post as vice president of the National Assembly, and last week the measures against Rainsy were initiated.

Rainsy's Facebook posting said such actions "practically concluded the elimination of the only opposition party represented in Parliament and show that Cambodia is now back to a one-party system like before the signing of the 1991 Paris Peace Agreements."

He charged that the ruling party's moves "represent a constitutional coup with the same legal and political consequences as the military coup they staged on 5-6 July 1997: a derailment of the democratization process as guaranteed in the Paris Agreements signed by 18 friendly countries under the aegis of the United Nations."

After the warrant was issued for his arrest, Rainsy said he would try to rally international pressure to get Hun Sen's government to back down. The government's action was already criticized by the United States and other nations, and on Tuesday a spokesman for U.N. Secretary-General Ban Ki-moon said he described the arrest warrant and earlier actions as a "worrisome development."

"The Secretary-General urges the Cambodian People's Party and the Cambodia National Rescue Party to resume their cooperation and dialogue and encourages all political players to refrain from violence, intimidation and harassment. A non-threatening environment of democratic dialogue is essential for political stability and a peaceful society," a U.N. statement said.