Hong Kong has banned non-residents from entering the city from four African countries and plans to expand that to travelers who have been to Australia, Canada, Israel and six European countries in the past 21 days due to fears over Omicron.

The World Health Organization said on Monday the Omicron coronavirus variant carried a very high risk of infection surges, and countries around the world have tightened travel restrictions.

In a statement late on Monday, the Hong Kong government said non-residents from Angola, Ethiopia, Nigeria and Zambia would not be allowed to enter the global financial hub as of November 30. Residents can return if they are vaccinated but will have to quarantine for seven days in a government facility and another two weeks in a hotel at their own cost.

"Non-Hong Kong residents from these four places will not be allowed to enter Hong Kong," the statement said. "The most stringent quarantine requirements will also be implemented on relevant inbound travelers from these places."

Additionally, non-residents who have been to Australia, Austria, Belgium, Canada, the Czech Republic, Denmark, Germany, Israel, and Italy in the past 21 days would not be allowed to enter the city from December 2. Vaccinated residents returning from these countries will have to do three weeks of hotel quarantine.

Hong Kong last week banned non-Hong Kong residents arriving from South Africa, Botswana, Eswatini, Lesotho, Malawi, Mozambique, Namibia and Zimbabwe.

Authorities have detected three people with the Omicron variant through mandatory testing while in quarantine, but it has no known coronavirus cases in the general community.