Police in Guangzhou have vowed to intensify efforts to crack down on illegal immigration, despite a protest by dozens of African people on Wednesday.

Police have launched a special campaign since the end of May to closely inspect living and business areas of foreigners, said He Jing, deputy director of the Guangzhou public security bureau.

Africans gather at a police station in Guangzhou. (Southern Metropolis Daily)

"Foreigners who have not applied for stay permits and hold fake or overstayed passports will be targeted," he said.

The campaign was a long-term task given that Guangzhou has developed into a major trade hub in South China for foreigners, especially those from Africa and the Middle East, he said.

But the regular inspection has triggered a recent brawl between police and foreigners.

On Wednesday afternoon, more than 100 African people protested outside a local police station in Guangzhou's downtown Guangyuanxi Road following unconfirmed reports that a Nigerian died after jumping out of a building to escape a passport check.

Police said in a press statement that only two African people were injured during the passport check; they are now in stable condition in a hospital.

One of the injured, who police said was involved in an illegal foreign exchange business, broke through a window and severely slashed his back in his escape attempt, the statement said.

"It was a regular passport check by police targeting foreign businessmen on Wednesday," an officer from the Guangzhou public security bureau, who declined to be named, told China Daily Thursday.

The check was also part of the police campaign to crack down on illegal activities committed by foreigners, he said.

Guangzhou Intermediate People's Court officials cite the so-called black money scam cases allegedly committed by eight foreigners from nine countries in the first half of this year as reasons for the crackdown.

Court officials said frauds committed by foreigners in Guangzhou so far this year totalled more than one-third of the cases between 2002 and last year.

To better serve foreigners, the entry and exit administrative authority has opened an online service for foreigners to apply for permit extensions, the local police authority said.

"Foreigners are warned to carry their passports. They should also pass registration procedures in relevant departments for staying and doing business here," he said.

More than 1 million foreigners enter or leave via Guangzhou ports each year, he said.

Sources with the Guangzhou Social and Science Academy said more than 20,000 African people with a stay permit for up to six months are living in Guangzhou.

"But the actual number of African people living here is bigger than the registered total. Many are living without passports or stay permits," Huang Shiding, a researcher with the academy, said.

Huang said many African people without a stay permit and visas have entered Guangzhou through neighboring Hong Kong and Macao special administrative regions.