Police raids on brothels in China have a pattern, sex workers say, often occurring a few days ahead of politically sensitive events or whenever someone in government orders an antipornography campaign to please the leadership.

It is during these times, the workers say, that their already miserable jobs grow more perilous with some police officers demanding steep bribes or sex, beating them, or locking them up for as long as two years without trial.

This is the life of prostitutes in modern China — a result of the Communist Party's long discomfort with sex, widespread corruption among authorities and rigid policies that put an already fragile population at even greater risk, according to a report released Tuesday by Human Rights Watch.