Prime Minister Hun Sen, accused of intensifying a crackdown on dissent before Cambodia's 2018 election, threatened on Wednesday to jail an opposition leader who has refused to come forward over an alleged sex scandal.
Political tensions have risen in recent months, with rights groups accusing Hun Sen's government of arresting scores of critics and tying up other opponents in legal cases.
The main opposition party's deputy leader Kem Sokha has spent the past month holed up inside his party's headquarters after armed police tried to arrest him in late May.
He is wanted for questioning in a prostitution investigation launched against a woman who claims to be his mistress.
But the lawmaker has refused to be interviewed, arguing that the police probe is politically motivated.
"You (Kem Sokha) said Hun Sen is scared of losing an election, but I send you a message: You could be jailed without release. A prisoner! Don't be rude," Hun Sen, who has ruled Cambodia for 31 years, told an audience in Phnom Penh.
"Even though you don't go to jail, still the jail could come to you. I am telling you in advance," he added.
The premier denied the prostitution case was politically motivated and said the lawmaker "created the problem himself by having a mistress".
The opposition Cambodia National Rescue Party could not be reached for comment.
Its top leader Sam Rainsy has been living in self-imposed exile for months to avoid arrest warrants he says are an attempt to undercut his party's prospects in the 2018 election.
The party has accused Hun Sen of denying it a majority by rigging the 2013 election in his favour, a charge the premier denies.
The wily and combative Hun Sen has steered impoverished Cambodia from the ashes of civil war to a relatively fast-growing economy.
But the opposition party has gained ground amid growing disillusionment with endemic corruption, rights abuses and political repression.
The European Parliament has threatened to review nearly $500 million of aid if Hun Sen's government continues to repress opponents, and the UN and United States have recently voiced concern over attempts to detain Kem Sokha.
But Hun Sen warned Wednesday against interfering in his country's domestic affairs.
"I don't want all diplomats to become parrots speaking the tone of the opposition party," he said. "Don't use so-called aid to insult Cambodia or to threaten Cambodia."