The first probable case of the Omicron variant of COVID-19 has been detected in Switzerland, the government said late on Sunday, as the country tightened its entry restrictions to check its spread.

The case relates to a person who returned to Switzerland from South Africa around a week ago, the Federal Office for Public Health said on Twitter.

Testing will clarify the situation in the coming days, it added.

Switzerland has ordered that travellers from 19 countries must present a negative test when boarding a fight to the country, and must go into quarantine for 10 days on arrival.

The list includes Australia, Denmark, Britain, Czech Republic, South Africa and Israel.

Swiss voters on Sunday backed the government’s pandemic response plan by a bigger than expected majority in a referendum, paving the way for the continuation of exceptional measures to stem the rising tide of COVID-19 cases. 

Some 62.01% voted in favour of a law passed earlier this year to provide financial aid to people hit by the COVID-19 crisis and laying the foundation for certificates giving proof of COVID-19 vaccination, recovery or a negative test. These are currently required to enter bars, restaurants and certain events.