Police in Beijing on Tuesday launched a 100-day campaign urging citizens to report on foreigners illegally living or working in the capital, after a British man allegedly tried to rape a woman.

It is unclear whether the crackdown is directly linked to the alleged sexual assault last week, which was purportedly caught on video and posted online, drawing millions of views and angry comments.

"The Beijing police department will... increase efforts to punish foreigners illegally entering, illegally living and illegally working in Beijing," it said on its official microblog page.

"At the same time, Beijing police will collect information from the city's many citizens," it added, posting a phone number for residents to call and report any suspicious activity.

A poster publicising the crackdown and illustrated with a giant fist was attached to the statement.

The Chinese capital is attracting an ever-increasing number of foreigners interested in work opportunities brought about by the nation's rapid economic growth, as compared to stagnant job markets back home.

According to the state-run Beijing Morning Post, which quoted police authorities, there are on average almost 200,000 foreigners in the capital on any given day -- including long-term residents and short-term visitors.

Foreigners living in the capital need an official residence permit, and those working in Beijing must have a visa that allows them to do so. But some do odd jobs on tourist visas, which is considered illegal in China.

In its report, the Beijing Morning Post quoted police as saying that foreigners caught in the crackdown would be fined or detained, and may also be ordered to leave China.

"In serious circumstances that constitute a crime, they will be held criminally responsible in accordance with the law," they said.

It is unclear what has become of the British man accused of trying to rape a Chinese woman, after he was detained last week. The British embassy in Beijing was not immediately available for comment, nor was the police.

Web-users broadly welcomed the crackdown on Tuesday.

"Leaving aside whether they act violently without any consideration, those (foreigners) who should leave must leave. Not only in Beijing but in the whole country.

"If it was Chinese people abroad, they would have been deported a long time ago," said one on Sina's popular microblog.