Omicron variant spreads to more countries as world on alert

A person queues to be tested for Covid-19 in Johannesburg, South Africa (Jerome Delay/AP)

The Omicron variant of the coronavirus has appeared in an increasing number of European countries, leaving governments around the world scrambling to stop the spread.

The UK on Saturday tightened its rules on mask-wearing and on testing of international arrivals after finding two cases.