Hong Kong is among the latest to expand travel curbs. In a late Monday statement, city authorities said non-residents from Angola, Ethiopia, Nigeria and Zambia would not be allowed to enter as of Nov. 30.
"The most stringent quarantine requirements will also be implemented on relevant inbound travellers from these places," the statement said.
Additionally, non-residents who have been to Austria, Australia, Belgium, Canada, the Czech Republic, Denmark, Germany, Israel and Italy in the past 21 days, would not be allowed to enter the city from Dec. 2, it added.
The global financial hub, among the last places in the world pursuing a zero-COVID strategy, earlier banned non-residents arriving from South Africa, Botswana, Eswatini, Lesotho, Malawi, Mozambique, Namibia and Zimbabwe.
In Australia, the five travellers with Omicron are all vaccinated and in quarantine, health officials said, adding they are asymptomatic or display very mild symptoms.
Canberra delayed on Monday the reopening of the nation's borders for international students and skilled migrants, less than 36 hours before they were due to be allowed back in.
"We're doing this out of an abundance of caution but our overwhelming view is that whilst (Omicron) is an emerging variant, it is a manageable variant," Federal Health Minister Greg Hunt told a media conference in Canberra.
Growing hopes that Omicron will be milder than feared have helped restore some calm to markets this week, after a rout on Friday that saw roughly $2 trillion being wiped off the value of global stocks.
Traders also took comfort from remarks by President Joe Biden that the United States would not reinstate lockdowns.
"This variant is a cause for concern, not a cause for panic," Biden said in remarks at the White House.
"We're going to fight and beat this new variant."
(Reporting by Marius Zaharia in Hong Kong, Renju Jose in Sydney and Reuters bureaus; Wtiting by Himani Sarkar; Editing by Shri Navratnam) ((firstname.lastname@example.org))