PHNOM PENH (Reuters) - A prominent deputy of Cambodia's opposition leader has left the country a day after Prime Minister Hun Sen threatened further arrests of opposition politicians.

Kem Sokha, leader of the opposition Cambodia National Rescue Party (CNRP), was arrested on Sept. 3, in a widening crackdown on critics of Hun Sen, which his opponents say is a ploy to win a general election next year.

The situation inside Cambodia was "very dangerous for CNRP leaders", Mu Sochua, 63, told Reuters via messages on social media site Facebook, adding that she had heeded the prime minister's threat and left the country on Tuesday (Oct 3).