LONDON (AP) — The new potentially more contagious omicron variant of the coronavirus popped up in more European countries on Saturday, just days after being identified in South Africa, leaving governments around the world scrambling to stop the spread.

The U.K. on Saturday tightened its rules on mask-wearing and on testing of international arrivals after finding two cases. New cases were confirmed Saturday in Germany and Italy, with Belgium, Israel and Hong Kong also reporting that the variant has been found in travelers.

Because of fears that the new variant has the potential to be more resis...