Omicron risks overloading health systems across Europe, the World Health Organization said, warning that more than half the region's population will be infected with the variant in the next two months.

Hans Kluge, WHO Director for Europe, said more than 7 million new cases were registered in the first week of 2022.

Kluge said the variant has now been reported in 50 of the 53 countries in the region and was becoming dominant in Western Europe. "At this rate, more than 50% of the population in the region will be infected with Omicron in the next six to eight weeks," he said - a rate of transmission he described as unprecedented.

Omicron's impact will be more deadly in countries where vaccination rates are lower, such as Central and Eastern Europe, Kluge predicted, saying he was "deeply concerned".

Omicron's greater transmissibility means authorities need to prepare for a mix of online and physical learning, Kluge stressed.