Hong Kong has begun culling 20,000 chickens and has suspended imports of fresh poultry from mainland China for 21 days after the discovery of the H7N9 bird flu virus in a batch of live chickens from the southern province of Guangdong.
The government order took effect on Tuesday, two days before celebrations begin for Chinese New Year, when poultry sellers generally anticipate a boom.
Authorities also ordered the closure of the wholesale poultry market, where the virus was discovered, until February 18 for cleaning and disinfection.
Local farms were banned from supplying live chickens to the market.
"Agriculture, Fisheries and Conservation Department officers will inspect all the local chicken farms and collect more samples for testing to ensure that local farms are not affected by H7 avian influenza," Dr Ko Wing-man, secretary for food and health, said in a statement.
The H7N9 virus passes between birds, but cases in humans have so far not shown evidence of sustained human-to-human infection, according to the World Health Organisation (WHO).
Experts have urged health authorities worldwide to be alert in detecting the H7N9 virus.
Two people infected with H7N9 bird flu have died in Hong Kong and a third patient is being treated.
All three were infected during visits to the southern Chinese city of Shenzhen.
The H7N9 bird flu virus emerged in March last year and has so far infected at least 240 people in China, Taiwan and Hong
Kong, according to the Hong Kong Department of Health.
China's official Xinhua news agency, citing the Chinese Centre for Disease Control and Prevention, said 19 people had died of the flu in China this year.
China's Health and Family Planning Commission reported a further nine cases of H7N9 bird flu to the WHO on Sunday and Monday.
Hong Kong last suspended live poultry imports in 2011 after a dead chicken tested positive for the H5N1 strain of bird flu
at the same market.