Singapore has detected its first locally transmitted case of the COVID-19 variant Omicron in a member of staff at the city state's airport, authorities said late on Thursday, warning that more Omicron cases are likely to be detected.

• WHO chief: Omicron may pose higher reinfection risk, but could be milder than Delta

The 24-year-old Singaporean woman, who works in a service role in the airport, "may have interacted with transit passengers from Omicron-affected countries," the health ministry said in a statement.

She tested preliminarily positive for Omicron as a part of the routine testing for frontline workers, it said, noting she was fully vaccinated and asymptomatic.

A second Omicron case reported on Tuesday was a traveler from Germany.

Both of individuals had received vaccine boosters shots, the health ministry said.

The cases are currently pending further genome sequencing to confirm the variant.

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Singapore had previously detected three Omicron cases, all found in overseas travelers.

"Given its high transmissibility and spread to many parts of the world, we should expect to find more Omicron cases at our borders and also within our community," the health ministry said.

Singapore has vaccinated 96% of its eligible population, and authorities are urging the public to get booster shots amid concerns over the Omicron variant. (Reporting by Chen Lin in Singapore Editing by Ed Davies)