The father of a Chinese man who died from the H5N1 strain of bird flu last week has also been diagnosed with the disease, authorities said on Friday.

The National Disease Authority has confirmed that a 52-year-old man surnamed Lu from the Nanjing, capital of the eastern province Jiangsu, was feverish with the H5N1 strain on Thursday, the Ministry of Health reported on its Web site (www.moh.gov.cn).

This latest case raises troublesome questions about how the man was infected.

Humans can contract H5N1 from close contact with infected birds, but scientists fear the disease could mutate into a version that spreads from person-to-person, risking wider outbreaks or even a global pandemic.

Lu's son died on Sunday from the same disease, making the question of how these two infections occurred especially important.

The Xinhua news agency had earlier reported that the son had had no contact with dead poultry and there had been no reported poultry outbreak in the province.

The latest report did not say whether contact with infected poultry had been confirmed in either of the infections.

With the world's biggest poultry population and millions of backyard birds roaming free, China is at the centre of the fight against bird flu.

This latest case brings the number of confirmed human infections of bird flu in China to 27. The Ministry of Health said the World Health Organisation had been notified of this latest case.

WHO representatives in Beijing could not be contacted for comment late on Friday evening.