A new report documents what it says are serious abuses by police against suspected female sex workers in China, including beatings, torture and arbitrary detention.
Human Rights Watch says much of the worst abuse happens during periodic, weeks-long anti-prostitution crackdowns when police raid massage parlors, night clubs, and other businesses.
One woman told the New York-based group that she was beaten until she turned "black and blue" because she would not admit to prostitution. Another said a police officer demanded sex in return for legal protection.
The report said these experiences reflect a wider problem. It accused the government of acting as if women who engage in sex work have "forfeited their rights."
Beijing officially outlaws prostitution, although sexual services are often openly sold on the street.
The report says suspected sex workers are often detained without due process for up to two years at "re-education through labor" camps and other facilities. Some women interviewed said they were lured into such centers and held for longer than they were originally told they would be.
Other women reported being subjected to questionable and humiliating health practices, such as forced HIV/AIDS testing. Many told Human Rights Watch they are afraid to seek medical attention or report sexual assaults for fear of being arrested or turned over to the police.
The group says Beijing's policies have failed to slow the sex industry. Instead, the trade has expanded rapidly in recent decades. It estimates there are four to six million sex workers in China, the majority of whom are women.