An opposition parliamentarian was arrested late Thursday and taken to a Cambodian military prosecutor's office, less than 24 hours after losing his immunity from prosecution, his party told AFP.
"Cheam Channy has been arrested just minutes before 7 pm (1200 GMT)," said Ung Bun Ang, spokesman for the Sam Rainsy party.
Cambodia's government has accused Cheam Channy of allegedly building an army as part of a coup plot. Analysts have dismissed the existence of such an army as extremely unlikely.
Cheam Channy had spent the day at his party's office, but when he headed home, military police surrounded him, the spokesman said.
He was taken to a military court, where he was shown an arrest warrant at the prosecutor's office, the spokesman added.
His arrest came the same day that lawmakers voted in a closed-door session to strip him, party leader Sam Rainsy, and fellow deputy Chea Poch of their immunity from prosecution.
Sam Rainsy left Cambodia just hours later, the party said.
He and Chea Poch face defamation suits brought by government officials.