BEIJING (AFP) - China has rejected a study which found a probable case of human-to-human bird flu transmission in the country, state media reported.

The study, published in British medical magazine The Lancet this week, said a 24-year-old man was likely to have infected his father with H5N1 before dying, raising the spectre of a feared flu pandemic.

But health ministry spokesman Mao Qun´an said there was no clear evidence to support the findings.

"So far no evidence has been found in China to support the idea that the H5N1 virus can easily pass from one person to another," he said, according to Xinhua news agency on Friday.

The case, in the eastern city of Nanjing in December, is one of a handful worldwide in which the H5N1 virus is suspected to have spread from one person to another.

To date, however, all such cases have been what scientists call "limited, non-sustained, person-to-person transmission," meaning that contagion only occurs under specific circumstances.

The vast majority of the known 378 human cases of H5N1 bird flu since 2003 were spread by domestic or wild fowl, according to the World Health Organisation. More than 60 percent proved fatal.

Experts fear that the H5N1 virus could mutate after infecting one human into a more contagious form, as occurred during at least three flu pandemics in the 20th century.

An estimated 20 to 40 million people perished in the so-called "Spanish flu" of 1918. Since 2003, there have been around 200 bird flu fatalities, mainly in Asia.