A Frenchman has been arrested for allegedly soliciting sex with a child prostitute, Cambodian police said on Monday.

Police said they found Olivier Madrieres (48) at a guesthouse on Saturday in the Cambodian capital Phnom Penh.

"He was arrested while he was having sex with a prostitute," said Keo Thea, chief of the municipal anti-trafficking and juvenile police unit.

Madrieres, who arrived in Cambodia last month as a tourist, was being held on charges of soliciting sex from the 15-year-old girl and faces up to five years in jail if convicted, Keo Thea said.

Cambodia has struggled to shed its reputation as a haven for paedophiles, putting dozens of foreigners in jail for child sex crimes or deporting them to face trial in their home countries since 2003.