HONG KONG (REUTERS) - Hong Kong authorities have confirmed the first human bird flu infection for this season after an elderly man who had recently travelled to mainland China was diagnosed with the deadly H7N9 virus strain.

The 75-year-old male patient, who had visited the southern Chinese town of Changping in Dongguan city this month before returning to Hong Kong, is in serious condition, the government said in a statement released late on Monday (Dec 19).

The case came to light as South Korea and Japan ordered further culls on Monday to contain outbreaks of a different strain of bird flu, having already killed tens of millions of birds in the past month.

Hong Kong has been battling sporadic cases of avian influenza in humans since the first outbreak killed six people in the Asian financial hub in 1997.

Macau, a former Portuguese colony an hour away from Hong Kong by ferry, culled about 10,000 chickens last week after a wholesale poultry market worker fell ill with the H7N9 strain.

The city temporarily suspended importing poultry from mainland China but resumed trade on Sunday.