Police in China seized one ton of fake Viagra pills during a series of raids on gangs that were making counterfeit drugs to sell domestically and overseas.

File photo of a police officer showing fake Viagra that was seized in raids in Beijing. [Agencies]

Aside from the the popular anti-impotency drug, fake versions of Tamiflu, which is being stockpiled around the world for a potential bird flu pandemic, and anti-malarial medications were uncovered, Xinhua news agency said Wednesday.

Four gangs were busted making the drugs during a two-year crackdown that involved Chinese and US authorities, as well as Interpol, Xinhua said, citing the Ministry of Public Security.

The announcement of the busts come after the former head of China's food and drug watchdog Zheng Xiaoyu was executed this month for taking bribes to approve medicines, some of which were unsafe.

The one ton of Viagra was uncovered in China's southern Guangdong province that borders Hong Kong following a raid late last year made in co-operation with US law authorities, Xinhua said.

The Tamiflu raids in May also took place after acting on intelligence from US authorities, resulting in the arrests of 19 suspects. Xinhua said the gang had been trying to sell the Tamiflu into the United States via the Internet.

Few other details of the busts, or the expected trials of the suspects, were revealed.