The University of Hong Kong (HKU) has successfully isolated the Omicron strain of the coronavirus from clinical specimens, HKU's Department of Microbiology said on Tuesday.

This is the first known research team in Asia to successfully isolate the Omicron variant.

"The HKU team succeeded in isolating the variant late Monday, four days after the first two Omicron cases were confirmed in Hong Kong on November 25, and five days after the variant was first reported to the World Health Organization (WHO) from South Africa on November 24," it said in a statement.

"Isolating the variant is the first step in the urgent study of the variant," said Kwok-yung Yuen, chair of infectious diseases at HKU's microbiology department, who led the research.

The virus will be further isolated and purified for research purposes, according to the statement.

The research team is working on assessing the virus' transmissibility, immune evasion capability and pathogenicity in animal models, as well as researching how to develop and produce inactivated vaccines against the variant.

Virus isolation and incubation were conducted at the biosafety level 3 laboratory of HKU.

Hong Kong recorded its third case of the Omicron variant on Tuesday, a 37-year-old man from Nigeria who arrived in the city on November 24 and quarantined in a designated hotel.

Hong Kong expanded a ban on entry for non-residents from several countries as global health authorities raced to curb a potential outbreak of the Omicron variant.

Omicron – first reported in southern Africa and which the WHO said carries a "very high" risk of infection surges – has triggered global alarm since last week.