Tighter COVID-19 restrictions are returning in countries across Europe as case counts rise from the quickly spreading and highly transmissible Omicron variant.

Threat level: Hans Kluge, the World Health Organization's Europe chief, said Tuesday that governments should prepare for "a significant surge" in COVID-19 cases, as Germany and Portugal became the latest countries to announce new measures.

The big picture: Several European countries announced plans to impose further pandemic measures after Christmas, but Sweden will from Wednesday require bars and restaurants to only serve seated guests, and Finland's bars and restaurants will shut at the earlier time of 10pm from Christmas Eve, per the BBC.

Germany will from Dec. 28 limit private gatherings to 10 people, shut nightclubs and require soccer matches to be played behind closed doors, DW.com reports.

Portugal will from Dec. 26 through at least Jan. 9 require bars and nightclubs to remain closed and the country will limit outdoor gatherings to 10 people per group on New Year’s Eve, the Guardian notes.

The Netherlands announced last Saturday a nationwide lockdown effective on Sunday, and all nonessential stores, bars and restaurants will be closed until Jan. 14, AP reports.

France and Austria tightened travel restrictions, while Paris canceled its New Year's Eve firework celebration, per AP.

In Denmark, theaters, concert halls, amusement parks and museums have all closed.

Ireland set an 8pm local time curfew on pubs and bars.

United Kingdom residents are required to wear masks indoors and show proof of vaccination or a negative coronavirus test to attend a nightclub or large event.

"Scotland, Wales and Northern Ireland have all announced curbs on social mixing," the BBC reports.

Go deeper: The UK's Omicron warning for America

Editor's note: This story has been updated with details on measures in the Netherlands, Germany, Portugal, Sweden, Finland, Scotland, Wales and Northern Ireland.