But indicating that such curbs may not stem the spread of the variant, Britain said on Saturday it had detected two cases and authorities in Germany and the Czech Republic also said they had suspected cases.
Omicron, dubbed a "variant of concern" by the World Health Organization, is potentially more contagious than previous variants of the disease, although experts do not know yet if it will cause more or less severe COVID-19 compared to other coronavirus strains.
The variant was first discovered in South Africa and had also since been detected in Belgium, Botswana, Israel and Hong Kong.
Dutch authorities said that 61 out of around 600 people who arrived in Amsterdam on two flights from South Africa on Friday had tested positive for the coronavirus. Health authorities were carrying out further tests to see if those cases involved the new variant. read more
One passenger who arrived from South Africa on Friday, Dutch photographer Paula Zimmerman, said she tested negative but was anxious for the days to come, having spent hours on a flight that likely had many infected passengers.
"I’ve been told that they expect that a lot more people will test positive after five days. It's a little scary the idea that you’ve been in a plane with a lot of people who tested positive," she said.
Financial markets plunged on Friday, especially stocks of airlines and others in the travel sector, as investors worried the variant could cause another surge in the pandemic and stall a global recovery. Oil prices tumbled by about $10 a barrel.
The Dow Jones Industrial Average closed down 2.5%, its worst day since late October 2020, and European stocks (.STOXX) had their worst day in 17 months.
It could take weeks for scientists to fully understand the variant's mutations and whether existing vaccines and treatments are effective against it. Omicron is the fifth variant of concern designated by the WHO.
Although epidemiologists say travel curbs may be too late to stop Omicron from circulating globally, many countries around the world - including the United States, Brazil, Canada and European Union nations - announced travel bans or restrictions on southern Africa on Friday.
On Saturday, Australia said it would ban non-citizens who have been in nine southern African countries from entering and will require supervised 14-day quarantines for Australian citizens and their dependents returning from there. read more
Japan said it would extend its tightened border controls to three more African countries after imposing curbs on travel from South Africa, Botswana, Eswatini, Zimbabwe, Namibia and Lesotho on Friday.
South Africa is worried that the curbs will hurt tourism and other sectors of its economy, the foreign ministry said on Saturday, adding the government is engaging with countries that have imposed travel bans to persuade them to reconsider. read more
The two linked cases of the new Omicron coronavirus variant detected in Britain were connected to travel to southern Africa, health minister Sajid Javid said.
Britain said it was expanding its "red list" to put travel curbs on more southern Africa countries, while South Korea, Sri Lanka, Thailand, Oman and Hungary also announced travel restrictions on southern African nations.
A minister in Hesse state said on Saturday that the variant had very probably arrived in Germany, in a traveller returning from South Africa. Czech health authorities said they were examining a suspected case of the variant in a person who spent time in Namibia.
Omicron has emerged as many countries in Europe are already battling a surge in COVID-19 infections, and some have re-introduced restrictions on social activity to try to stop the spread. Austria and Slovakia have entered lockdowns.
The new variant has also thrown a spotlight on disparities in how far the world's population is vaccinated. Even as many developed countries are giving third-dose boosters, less than 7% of people in low-income countries have received their first COVID-19 shot, according to medical and human rights groups.
Seth Berkley, CEO of the GAVI Vaccine Alliance that with the WHO co-leads the COVAX initiative to push for equitable distribution of vaccines, said this was essential to ward off the emergence of more coronavirus variants.
“While we still need to know more about Omicron, we do know that as long as large portions of the world’s population are unvaccinated, variants will continue to appear, and the pandemic will continue to be prolonged," he said in a statement to Reuters.
"We will only prevent variants from emerging if we are able to protect all of the world’s population, not just the wealthy parts."