A Cambodian court has issued a summons for opposition leader Sam Rainsy to hear defamation charges, adding to legal troubles that already include another summons and an arrest warrant.

Rainsy has been in self-imposed exile since mid-November, when an order for his arrest was issued on an old conviction for defaming Cambodia's foreign minister. He also was expelled by the ruling party-dominated National Assembly, losing his parliamentary immunity. It had been generally assumed that the conviction had been lifted by a 2013 pardon.

Lawyer Ky Tech said Wednesday that he filed a complaint with a Phnom Penh court on behalf of the National Assembly president, Heng Samrin.

Rainsy's supporters believe his legal problems are orchestrated by Prime Minister Hun Sen in response to the opposition's growing political strength.