Experts on Beijing's public-security operations have urged authorities to do more about the influx of foreign sex workers, after the arrest of four foreign women at a downtown club.

Police raided Qixingdao bar in Chaoyang district on July 18 and arrested 15 suspected prostitutes, including the four foreigners, according to a statement by the Public Security Management Corps under the Beijing Public Security Bureau on Tuesday.

Located in the basement of Huasheng International Mansion, an office building close to many embassies, the bar was closed on Tuesday. An employee of a warehouse next door who did not want to be identified said it will stay shut for two months.

A sign for the bar, written in Chinese and other languages, still hangs on a wall outside the building.

Ou Yang, a publicity officer for the Public Security Management Corps, said the arrests were part of a citywide campaign that started in April 2010 targeting entertainment venues that allow obscene shows or prostitution.

"During previous investigations, we found the bar (Qixingdao) was used by foreign prostitutes, and employees there also knew about the prostitution," he said. "Those foreigners could communicate with customers in gestures and simple Chinese to indicate that they were prostitutes.

"Some cars parked at the gates were used to take the foreigners and customers who made a deal in the bar to hotels or other places."

Ou did not disclose further information about the arrested women, including their nationalities.

A police officer stationed in Sanlitun, an area popular among foreigners for its bars and restaurants, said his office has assigned three officers to target prostitution since the campaign started.

"The officers investigate bars and entertainment venues randomly and also collect clues from venue owners or residents," he said, speaking on condition of anonymity.

As China has opened its door to the world, the capital has seen an influx of foreign sex workers to the point that it is now a serious problem, said Dai Peng, director of the criminal investigation department at Chinese People's Public Security University.

While some women are the victims of sex traffickers, others are working in the sex industry willingly because they can earn more money that way than in their own countries, he said. Many of the willing prostitutes are in China on student, tourist or temporary-worker visas.

"Meanwhile, prostitution has developed in a concealed way. People prefer to contact prostitutes through the Internet, which is difficult for police to investigate," he said.

Wang Hongjun, director of the university's public-security management research department, said that foreigners working as prostitutes happens not only in big cities like Beijing and Guangzhou, but also in smaller areas.

"The majority of foreign sex workers are from neighboring countries, such as Russia and Vietnam, and entertainment venues and hair salons are still the main places where the prostitution occurs," Wang said.

He spoke highly of the campaign on prostitution in the capital, but said the crackdown can solve the problem only on the surface, and it can't deal with the root causes.

Both Dai and Wang urged exit-entry administrations to make stricter checks of foreigners' backgrounds and why they want to come to China.

"After foreigners enter our country, police and administrators should pay more attention to their visa deadlines and urge them to update certificates if they want to stay longer," Dai said, adding that foreigners will get the same punishment as Chinese if they are found to be involved in prostitution.

Prostitution is illegal in China. People face an administrative detention of 15 days if found working as prostitutes. Employees of businesses involved in prostitution are obligated to report it.

However, Dai added, a thorny problem now is how to balance development of the entertainment business against the prostitution crackdown.

"After all, an entertainment venue's business will be affected if it is related to prostitution," Dai said.

In April 2010, police arrested more than 1,100 people who were allegedly engaged in prostitution and shut down many Beijing venues, including the Heaven Earth nightclub, the No 8 Club KTV and the Sunworld Dynasty Hotel KTV.

Li Yu contributed to this story.

Contact the writer at caoyin@chinadaily.com.cn.