BEIJING (AFP) - China has made good progress in developing a human vaccine against the deadly bird flu virus, with a second phase of tests showing it to be safe and effective, state press reported Monday.

About 400 people aged between 18 and 60 who were given the vaccine between September and November this year had shown no ill side effects, and the drug had "performed well", Xinhua news agency said, citing an official involved.

"China is capable of producing bird flu vaccines for humans in appropriate quantities," Zhang Jiansan, the vice general manager of Beijing-based vaccine producer Sinovac Biotech, was quoted as saying.

The World Health Organisation gave a cautious response to the announcement.

"Around a year ago China announced the first phase of clinical tests for a human vaccine," a Beijing-based WHO spokeswoman said in an e-mail to AFP.

"It´s encouraging that China is making progress but WHO needs more information to properly comment. We´ll be talking to the Chinese researchers for more information."

Many countries and firms have been developing vaccines to combat the H5N1 strain of the bird flu, which has killed more than 200 people worldwide, mostly in Southeast Asia, since late 2003.

Seventeen people have died of the bird flu in China.

Scientists have warned that the virus could kill many more people around the world if it mutates into a form that can be easily passed among humans, rather than from poultry to people as is now the case.

But WHO assistant director general David Heymann said this month in Geneva there was no need yet for a massive vaccine campaign against the bird flu virus because it has not been proven that it would become a pandemic.