HAVANA, Nov 29 (Reuters) - Cuba will ratchet up restrictions from Dec. 4 on passengers from certain African countries over concerns about the Omicron coronavirus variant, the country"s Communist-run government said on Monday. The World Health Organization said on Monday that the Omicron variant carried a "very high" risk of infection surges. Countries have been imposing fresh travel restrictions in recent days in response to the discovery of the variant.Travelers arriving from South Africa, Botswana, Lesotho, Eswatini, Zimbabwe, Namibia, Malawi, and Mozambique will be allowed to enter Cuba, the country"s health ministry said, but will be required to comply with multiple precautionary measures, including proof of vaccination, three PCR tests and a seven-day quarantine. Travelers from other sub-Saharan African nations, as well as Belgium, Israel, Hong Kong, Egypt and Turkey will be required to take two PCR tests, the ministry said.Concerns over the Omicron variant are flaring in Cuba just two weeks after the Caribbean island nation reopened its borders to international visitors. Cuba, whose economy depends on tourism, eased entry requirements after inoculating most of its people with a COVID-19 vaccine developed domestically. New infections have dropped off sharply in recent weeks, as have deaths from COVID-19.