Condom advertisements are designed to curb the spread of HIV

It is one reason why more than 10% of China's population are thought to be carriers of the hepatitis B virus - a figure higher even than sub-Saharan Africa.

Even more worrying is the effect such illegal recycling of syringes could have on the spread of the HIV virus that causes Aids.

The government has not said how widespread it believes the problem to be, but the market for such medical equipment runs into billions of US dollars.

In one case alone, police in eastern China recently seized and destroyed 10 tonnes of used syringes.

Health system in chaos

The break-up of China's old centrally-controlled economy has left its health-care system in chaos and hospitals desperately short of cash.

It has led to the growth of an underground market in all sorts of medical products.

Last year the government had to ban hospitals from paying for donated blood after a number of patients were infected with the HIV virus from blood transfusions.

It turned out that the blood had come from illegal blood banks. It had not been screened, and many of the donors were intravenous drug-users.