A Hong Kong man infected with the deadly H7N9 bird flu died late Monday, less than a week after he was confirmed to be infected with the deadly virus, authorities said.

The 65-year-old man was the second person to die from the virus in Hong Kong, and the third reported case of H7N9 infection.

"The patient passed away at 7:02pm tonight," a government statement released late Monday said.

Initial investigations showed that the man had travelled to the neighbouring mainland Chinese city of Shenzhen a week before he was infected.

He had not been directly exposed to live poultry, but had probably contracted the virus outside the city, Hong Kong Centre for Health Protection controller, Leung Ting-hung, had told reporters last week.

"Our initial investigation has revealed that the patient traveled to Lowu, Shenzhen with a family member from January 1 to 2. He passed by a wet market which sold live poultry in Lowu on January 1," Leung had said.

Five close contacts of the man remain under quarantine, with 98 other contacts, including healthcare workers and others, under medical surveillance.

An 80-year-old man died on Boxing Day last year after he was infected with H7N9, Hong Kong's first death from the virus.

The case was the second reported incidence of H7N9 infection in the city after a 36-year-old Indonesian domestic helper was diagnosed in early December.

Hong Kong is particularly alert to the spread of viruses after an outbreak of Severe Acute Respiratory Syndrome (SARS) swept through the city in 2003, killing 299 people and infecting around 1,800.

The H7N9 outbreak began in China in February 2013 and reignited fears that a virus could mutate to become easily transmissible, potentially triggering a pandemic.

As of January 12, a total of 169 human cases of avian influenza H7N9 have been confirmed on the mainland.