The ban by Hong Kong applies to Australia, Canada, France, India, Pakistan, Philippines, UK and US.
Hong Kong announced strict new anti-coronavirus controls on Wednesday, banning flights from eight nations, shuttering bars and gyms and cancelling evening restaurant dining after the Omicron variant was detected within the city.
The restrictions are the latest economic blow to an international business hub pursuing a zero-Covid strategy that has kept cases low but left residents cut off from the rest of the world.
Like mainland China, Hong Kong has maintained some of the world's harshest measures throughout the pandemic -- including virtually closed borders, weeks-long quarantines, targeted lockdowns and mass testing.
The city has recorded 114 Omicron cases as of Tuesday evening, with the vast majority identified at the airport or during the 21-day hotel quarantine that is mandatory for most arrivals.
But a small community outbreak traced to Cathay Pacific airline staff in recent days has sparked the imposition of tough new measures. Chief executive Carrie Lam said health officials now fear the contagious variant was silently spreading within the community.
"We have cases that have their sources identified but not the route of transmission," she told reporters. Flights from Australia, Canada, France, India, Pakistan, the Philippines, UK and US will be banned from midnight on Saturday for two weeks.
All large-scale public events will be cancelled while from Friday over a dozen types of businesses, including bars, nightclubs, gyms, and beauty parlours, will have to close.