13 cases of Omicron strain have been reported in the Netherlands

The new Omicron coronavirus variant kept spreading around the world on Sunday, with 13 cases found in the Netherlands and two each in Denmark and Australia, even as more countries tried to seal themselves off by imposing travel restrictions.

Health officials in Australia’s most populous state, New South Wales, said two passengers who arrived in Sydney from southern Africa on Saturday evening had tested positive for the variant.

Countries have imposed a wave of travel bans or curbs on southern Africa to try to stem the spread.

In Britain, where two linked cases of Omicron identified on Saturday were connected to travel to southern Africa, the government announced measures to try to contain the spread, including stricter testing rules for people arriving in the country and requiring mask wearing in some settings.

Although epidemiologists say travel curbs may be too late to stop Omicron from circulating, many countries - including the United States, Brazil, Canada, European Union nations, Australia, Japan, South Korea and Thailand - have announced travel bans or restrictions on southern Africa.