A French architect held in Cambodia for more than a month has been released and flown to China, where he is wanted as a witness in connection with the country's biggest political scandal in year.

Cambodian officials said Wednesday that Patrick Devillers boarded a flight late Tuesday under is own free will.

Devillers was arrested last month at China's request but never charged.

He is said to have had a close business relationship with ousted Chinese Communist Party official Bo Xilai, and his wife, Gu Kailai.

Bo was fired as party chief of the city of Chongqing earlier this year as part of a massive corruption probe, while his wife is under investigation in the murder of a British businessman.