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.

- Business restrictions -

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.

Dining inside restaurants will be banned after 6:00 pm.

All cruises have also been cancelled -- on Wednesday a ship carrying 3,700 passengers and crew returned to port for mass testing after nine people were traced as close contacts of an Omicron case.

Hong Kong has bounced between heavy and light social distancing restrictions throughout the pandemic.

Compulsory mask-wearing, limits on more than four people gathering in public and restaurant quotas have remained even during periods when no local cases were detected for weeks at a time.

The restrictions have hammered the tourist and bar sectors and left international businesses struggling to retain and recruit talent.

The catering sector had a torrid 2020 but largely bounced back last year as residents flocked to local restaurants and hotels.

Hong Kong's strict rules have kept the city enviably free of the virus, with just over 12,000 cases and 213 deaths since the pandemic began.

Lam has said that resuming travel routes with mainland China must come before reopening to the rest of the world.

But there has been little concrete progress on that front and the latest outbreak has once again caused a setback.

Hong Kong's ability to reopen has also been hampered by poor vaccine takeup.

Despite ample supplies, only 70 percent of Hong Kongers have chosen to have two doses and the rates among the elderly -- the demographic most likely to die in the event of an outbreak -- is far lower.