HONG KONG (BLOOMBERG) - Airlines in Hong Kong were informed that crew working on non-China passenger flights have lost all quarantine-related exemptions, the South China Morning Post (SCMP) reported, dealing another blow to carriers reeling as the city's borders remain largely closed.

Hong Kong's government told airlines of the latest changes to its rules earlier on Wednesday (Dec 29) before the measures went into effect at midnight, the newspaper said, citing unidentified sources.

The move comes after the authorities on Tuesday mandated three-day hotel quarantines for air-cargo crew.

Other changes include necessitating that non-mainland China flights to and from Hong Kong be operated by so-called "closed-loop" aircrew, who will be required to spend as many as two weeks in quarantine every time they land in the city, the SCMP said.

In the light of the new measures, Cathay Pacific Airways is consolidating its passenger flight schedule for January and affected customers can opt for full ticket refunds, a spokesman said in response to a query from Bloomberg News on Thursday, without elaborating.

"The further tightening of crew quarantine restrictions continues to constrain our ability to operate flights as planned," the spokesman said. "We are communicating with affected customers and will endeavour to make alternative flight arrangements for them."

A government spokesman did not immediately reply to a request for comment.

The Asian financial hub is imposing increasingly stringent border control measures as the highly transmissible Omicron variant spurs record case counts globally.

Hong Kong has some of the world's strictest quarantine requirements and has seen no local transmission of the virus since June, but concerns are mounting that it will be left behind as other major cities shift towards living with Covid-19 as endemic.

Hong Kong found suspected Omicron cases in two Cathay Pacific aircrew members this week.

They are suspected to have broken the airline's isolation guidance and been on multiple outings during their first three days after returning to Hong Kong from the United States, exposing the city to infection.

Cathay Pacific is already at risk of widespread flight cancellations in the coming days as it has been unable to secure enough quarantine hotel rooms for crew to meet the new rules, the newspaper said.

The airline operates many of its long-haul flights under a closed loop to avoid staff interacting with the local community.

The strategy will now be extended to flights across Asia and increase stress on operations, according to the SCMP report.

Hong Kong has announced that it will shut down flight routes for two weeks if multiple cases are found on any one route.

It has banned Cathay Pacific flights from Toronto and Los Angeles from Dec 29 to Jan 11, adding to a list of suspended routes ranging from London and Seoul to Dubai and Bangkok.