South Korea has stepped up customs inspections to stop the smuggling from China of pills made from dead human foetuses or deceased infants, a report said on Sunday.

The illegal importing to South Korea of "human-flesh" capsules -- taken by men who believe it enhances sexual performance but which could pose serious health hazards -- has increased since the first case was detected in August.

South Korean customs have so far uncovered 35 attempts to bring in a total of 17,451 capsules in travellers' luggage or by mail, the Yonhap news agency said.

The pills are contaminated with "super bacteria" and other disease-causing organisms, Yonhap said, quoting customs officials. Some pills were hidden in capsules of legitimate drugs to disguise their contents.

Yonhap quoted officials as saying they would strengthen inspections of drugs from the Chinese cities of Yanji, Qingdao and Tianjin, where many of the so-called "human-flesh" pills are believed to be produced.