Hong Kong on Wednesday reimposed some of its toughest COVID-19 restrictions, banning flights from eight countries including India until January 21, in a bid to arrest the rising number of omicron cases.

Hong Kong Chief Executive Carrie Lam Cheng Yuet-ngor announced that travellers from eight countries -- Australia, Canada, France, India, Pakistan, the Philippines, the UK and the US, including via transit -- are banned from returning to the city for two weeks starting Saturday, Hong Kong-based South China Morning Post reported.

Hong Kong is reimposing some of its toughest COVID-19 restrictions across the board covering social activities and international travel, setting a 6-PM curfew on all dine-in services and banning flights from eight countries as it braces for a fifth wave of infections amid Omicron fears, the Post report said.

Hong Kong, a major aviation hub and financial centre, is a Special Administrative Region of China.

Lam said that the tougher rules were necessary with the city on the verge of a wider coronavirus outbreak following the community detection of an unlinked Omicron case.

There has been rapid change in the pandemic situation which has caused us to be worried. We will announce today fast, decisive and precise measures to cut the transmission chains, Lam told reporters at a press conference.

The two-week ban on passenger flights will be effective until January 21.

Travellers who were recently in those countries or had transited through them will be barred from returning to the city for two weeks.

She said that the measures were vital for preventing imported cases especially infections carrying the highly transmissive omicron variant from spreading further in the community and to prevent public hospitals from being overloaded with COVID-19 patients.

Lam said she hoped affected businesses would understand the decisive, swift and sharp action taken to curtail the virus.

We will take bold and stringent measures so that within a very short period of time we can contain the Omicron variant, she said.

Leading microbiologist Professor Yuen Kwok-yung, declaring that a fifth COVID-19 wave was technically underway, said that a number of untraced cases were appearing in the community with health officials still scrambling to pin down their origin.

Fellow government adviser Professor Gabriel Leung, dean of the University of Hong Kong's faculty of medicine, estimated that it would take at least three to six months to fully control the epidemic if there was a community outbreak.

If so, the plan to open the border will once again fail, he said, amid a pending scheme to resume quarantine-free travel with mainland China.

On Wednesday, Hong Kong reported 38 COVID-19 cases, pushing the official tally to 12,799, with 213 related deaths, the Post report said.

India on Wednesday saw a single-day rise of 58,097 new coronavirus infections, the highest in around 199 days, taking the total tally of cases to 3,50,18,358. The active cases were recorded above 2 lakh after around 81 days, according to the health ministry.

The country's death toll has climbed to 4,82,551 with 534 daily fatalities, the data stated.

A total of 2,135 cases of Omicron variant of coronavirus have been detected, out of which, 828 have recovered or migrated, the ministry added.