Drug offences involving foreigners rose sharply last year, according to an official at the Ministry of Public Security.
Most of the foreign drug trafficking suspects caught are Africans, said Liu Yuejin, director of the ministry's narcotics control bureau.
The ministry said police handled 1,491 drug-related crimes involving foreigners last year, a year-on-year increase of 15.4 per cent. A total of 1,963 foreign drug suspects were arrested, an increase of 17.3 per cent.
Police also confiscated 5.9 metric tons of drugs, an increase of 31 per cent.
"Due to high market demand, the desire for profits, and loose management, foreign drug gangs are active in southern China, including Guangdong and Yunnan provinces and the Guangxi Zhuang autonomous region," Liu said.
African drug trafficking suspects smuggled heroin from the Golden Crescent region -the mountain valleys of Iran, Afghanistan and Pakistan - or brought marijuana or cocaine to China illegally from Africa and South America, Liu added.
Cui Qingchao, deputy director of the Guangzhou customs anti-smuggling department, said foreign traffickers obtained the drug methamphetamine cheaply in the Guangdong cities of Lufeng and Jieyang. They also hired unemployed locals and expectant mothers to transport drugs to other countries.
In addition, some African drug suspects have acted as "agents" for Pakistani drug lords, Cui said.
"After obtaining drugs from these drug lords, they usually hire foreign traffickers who hide the drugs in their bodies or luggage. They take the drugs to Beijing and Shanghai or send them to Guangdong and other provinces through express mail services," Cui added.
Liu said the authorities face challenges in curbing rampant drug trafficking rings headed by foreigners.
Further investigations and interrogation are difficult because of the language barriers, he said. Suspected traffickers also tend to use violence when police try to arrest them.
"Suspects often use African languages to contact each other to strike drug deals, so it's difficult to get intelligence and capture the drug lords, Liu said.
But he said the authorities will increase supervision of foreign residents, especially in Guangdong.
Wu Ming'an, a criminal law professor at China University of Political Science and Law, said drug checks must be stepped up by customs authorities and at airports and ports.