Fake drugs seized by the police during the "Thunder action", July 16. [Photo/Xinhua]

HANGZHOU - Chinese police have detained over 20 people in its latest crackdown on the production and online trading of fake drugs, the public security authorities in the eastern province of Zhejiang said Sunday.

Police seized at least 20,000 boxes of fake drugs and several tonnes of raw materials in the crackdown that lasted for more than three months, authorities in Zhejiang's Huzhou City said in a press release.

It said the drugs were sold to nearly 30 provinces and municipalities across China and the total selling price topped 100 million yuan (16.11 million US dollars).

Among the best-sold fake drugs were slimming capsules and painkillers that contained banned ingredients, the document said.

Most of them were allegedly "imported products" and were sold only at online stores on Wechat, China's most popular mobile messaging app.

Police said many customers complained of health problems after taking the drugs.

A 30-something woman surnamed Li said the slimming drugs she bought in March were quite effective at the beginning and she lost several kilograms.

"But in a few months, my heart rate was faster than normal, I lost my appetite and suffered insomnia," she said.

As complains mounted, police in Huzhou began to investigate an online store called "Liu Lulu Milk's Cosmetics", run by a woman surnamed Liu and her husband.

Behind the store was an illegal drug production and trading hierarchy that involved dozens of people working in Zhejiang and Guangdong provinces, police said.

Investigation is continuing.