MANILA - The Philippines and Cambodia on Wednesday (Dec 15) reported their first cases of the Omicron variant, fuelling unease across Asia and further dimming hopes of a recovery as the new year approaches.

Health officials in Manila said they found two travellers - one from Japan who arrived on Dec 1 and another from Nigeria the day earlier - carrying the Omicron variant. Both were asymptomatic.

Cambodia's Health Ministry said it detected the variant in a 23-year-old woman who returned from Ghana, via Dubai and Bangkok. She was 15 weeks pregnant.

Omicron has already spread to Singapore, China, Japan, South Korea and India, as well as Hong Kong and Taiwan.

The new cases in the region coincided with a World Health Organisation (WHO) warning that the variant is spreading at an unprecedented rate.

First detected in South Africa and Hong Kong, Omicron has now been reported in 79 countries, and is probably present in most other countries as well.

The variant "is spreading at a rate we have not seen with any previous variant", said WHO chief Tedros Adhanom Ghebreyesus.

He added that it should not be dismissed as "mild".

"Even if Omicron does cause less severe disease, the sheer number of cases could once again overwhelm unprepared health systems," he said.

Without giving specifics, Dr Tedros added: "Evolving evidence suggests a small decline in the effectiveness of vaccines against severe disease and death, and a decline in preventing mild disease or infection."

Independent researchers had warned on Tuesday that the Philippines could face a "serious surge" in Covid-19 cases should Omicron reach its shores.

Dr Guido David, a fellow at Octa Research, drew parallels to South Africa's experience with the variant.

He said that from fewer than 300 new cases a day, South Africa is now seeing close to 40,000.

"Although vaccine coverage in the Philippines is significantly higher compared with South Africa, the Omicron variant, if it enters the country's borders, will likely trigger a serious surge of new cases," he said.

News of the first Omicron cases sent Philippine stocks plummeting.

Mr Luis Limlingan, a stock analyst at Regina Capital Development, said: "Investors are now speculating as to whether the cases will be contained, and if the government will adhere to stricter measures to protect from cases increasing."

The Philippines has seen record low numbers in Covid-19 infections over the past month, with the daily average plunging to 91 in the first two weeks of December.

The government has responded by easing tough quarantine restrictions, while ramping up its vaccination drive. It has allowed seniors and minors to go out of their homes, and dropped a requirement for everyone to wear face shields. Cinemas and gaming arcades have also been reopened.

Huge crowds have since been flocking to malls, and social calls have become more frequent, as Filipinos ramp up their Christmas shopping and get-togethers.

Popular tourist destinations like the famed island resort of Boracay are seeing record bookings.

Officials say it is too early to begin tightening the screws again, without a clear trend of exponentially rising cases.

For now, the Philippines is bringing back testing and quarantine protocols for some 40 "green list" countries and territories, including China, Japan, Indonesia, Saudi Arabia and Hong Kong, which hosts large numbers of migrant Filipino workers.

Earlier this month, Manila allowed fully vaccinated travellers - but not tourists - from these countries with negative Covid-19 test results to enter the Philippines without needing to undergo quarantine for five days upon arrival. It now requires that they undergo quarantine and be retested on the fifth day.

The Philippines still has the second-worst outbreak in South-east Asia, with over 2.8 million cases and some 50,000 deaths.

Governments across Asia have also been enforcing strict border controls as Europe battles a fresh wave of infections and hospital admissions.

Early data suggests Omicron is more transmissible than the Delta variant and even those vaccinated may not be spared, though there is no proof yet that it causes more severe illness.

WHO's emergencies director Mike Ryan said: "The question is how much protection are the current vaccines that we are using, which are currently life-saving against all the variants, and to what extent do we lose any protection against severe illness and death against Omicron. The data is pointing towards there being significant protection."

Still, WHO urged countries to act swiftly to rein in transmission and protect their health systems, and warned against complacency.

WHO expert Bruce Aylward also warned against "jumping to a conclusion that this is a mild disease".

"We could be setting ourselves up for a very dangerous situation," he added.