HONG KONG (AFP) - Hong Kong will cull approximately 20,000 chickens after discovering the H7N9 avian influenza virus in a batch of poultry imported from mainland China, authorities said on Monday.

The positive reading came just days after the southern Chinese city introduced widespread testing of imported live poultry following growing public concern over the safety of imports, particularly from the mainland.

Two people have died from the human form of the virus in Hong Kong since the first infection was publicly reported in December.

On Friday, the city introduced a serological test for H7 avian influenza in live poultry and soon discovered a batch that tested positive for the virus.

"A government department has confirmed that the sample chicken from the chicken imported from the mainland tested positive for H7N9 avian influenza virus," Hong Kong health minister Ko Wing-man told reporters late on Monday.

"All the poultry in the wholesale market will be destroyed tomorrow morning...the total number of chickens concerned amounts to 20,000," Mr Ko said, declaring the market to be an "infected place".

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.