Beijing police have smashed three prostitution rings involving 83 people, the municipal Public Security Bureau said on Thursday.

More than 250 police officers in the capital, divided into 18 groups, arrested the 83 suspects in the city's Chaoyang district and in Xianghe, Hebei province, on April 10, the bureau said.

Among the suspects, three were organizers and 27 prostitutes from foreign countries, the police said, without disclosing the nationalities.

According to a statement provided by the bureau, police had been tracking the movements of a man nicknamed "A Long", who had attracted attention by posting prostitution cards at big hotels and restaurants across the city.

The case involving A Long was part of a campaign now under way that is aimed at fighting drugs, gambling and prostitution across the city.

Thirty-one people were arrested in Chaoyang district on suspicion of gambling on the evening of March 25, with the police confiscating gambling devices worth almost 300,000 yuan ($48,500).

So far, police have broken up 7,954 gangs suspected of those crimes, detaining 2,356 people and confiscating about 26 million yuan, a police statement said.

It added that as part of the campaign, employees in entertainment venues, such as KTV and night clubs, have been asked to swipe their identity cards when they arrive at work, and that bath houses and massage outlets now have separate accommodation for men and women.

The bureau already requires all travelers to register when they check in at premises, and all gaming machines must have licenses.

The number of cases related to such crimes have fallen by 50 percent in the past three years, according to statistics from the bureau.