In one of the largest stings of alleged brothels this year, officials raided two massage parlours in Phnom Penh on Thursday night and rescued 21 girls believed to have been trafficked, officials said.

The raid was conducted by Cambodia’s anti-trafficking police unit, juvenile protection officers and evangelical anti-trafficking NGO International Justice Missions.

A municipal police officer who was involved in the raids but declined to be named said police took 29 people out of both locations during simultaneous raids.

At the first parlour on Street 163 in Daun Penh district, officers rescued 10 sex workers and arrested three men. At the second location on Sothearos Boulevard in Chamkarmon district, police removed 11 sex workers and five men.

“We have been following this case with police for several months,” said John Roberts, director of IJM’s investigations unit. He added that police have not yet verified how many of the rescued girls are underage, but as many as 40 per cent of the sex workers in Cambodia are minors, according to NGO End Child Prostitution, Abuse and Trafficking in Cambodia.

The court had questioned six men arrested in the raid, said Ork Youran, a clerk of deputy prosecutor Chea Meth at the Phnom Penh Municipal Court.

IJM staff said they believed both parlours are part of a larger criminal network that brings Vietnamese girls to Cambodia as sex workers. Officials were alerted to the activities at the massage parlours by a client who was offered sexual services.

IJM has previously come under fire for using entrapment techniques to bust fraudulent businesses masking sex trafficking – a tactic that is now legal for drug busts, but not for anti-trafficking raids.

“IJM is currently talking with government officials at the ministry of justice and information to implement a good legal structure … that would give police the authority to use anti-trafficking tactics available to police in most countries in the world,” Roberts said.