Sophos’ spamtraps are picking up an increasing number of junk messages which claim to sell Tamiflu, the drug believed most effective at protecting humans from the H591 strain of the bird flu virus.

The drug is in high demand because of fears that the virus could become a pandemic, and spread further around the world following deaths in Asia.

The spam e-mails urge recipients to protect themselves and their families from the avian flu virus by purchasing Tamiflu from an online website.

The website users can link to also supposedly sells Viagra, and a number of other medications.

"It may make a change from receiving junk e-mail about Viagra, but you should never ever buy drugs online, as you could be putting your health in mortal danger. Spammers are not interested in people’s health, they’re only interested in making fat profits," said Graham Cluley, senior technology consultant at Sophos in a statement.

"Drugs like Tamiflu should be prescribed by legitimate doctors, not quacks on the Internet. Buying medicine online, from a website advertised by spam e-mail, is like playing Russian Roulette."

Representatives of Roche, the Swiss pharmaceutical company Roche which produces Tamiflu, say they have received reports of internet sales of drugs which purport to be Tamiflu but are in fact bogus.

The American Medical Association and British Medical Association are campaigning to alert consumers about the risks of purchasing drugs online.

"You can never be sure that the drugs you buy online are the real thing," warned Cluley. "In your attempt to look after your health, you could actually be putting it at even greater risk."

Earlier this year an international spam gang was hit by a lawsuit forcing them to shut down a network of websites peddling porn and bogus prescription drugs.