The World Health Organization (WHO) in Europe on Thursday said they were seeing an "explosion" of virus cases in the European region and warned mortality rates were also rising.

"We do see an explosion.... in the sense it only takes a couple of days to have over the European region an increase of one million cases," WHO's regional director for Europe Hans Kluge told AFP.

And while the mortality rate could also be seen rising "little by little", Kluge cautioned that closing schools should be seen as a last resort.

"We need to keep the schools open really until last because we cannot afford a Covid-19 lost generation," Kluge said.

However the regional director also said that the "status quo is not an option," and called for "proportionate targeted measures," which could be scaled up.

Kluge stressed that governments should take into account two things: "coherence, so people see that we don't flip-flop, and... predictability, so people know if this threshold is being reach, this is what is going to happen."

He also called for the widespread use of face masks.

"With general mask wearing and strict control of social gatherings we can save 266,000 lives by February in the whole European region," Kluge said.

WHO Europe includes 53 countries, including Russia and countries in Central Asia, and on Thursday reported a total of over 12 million cases recorded in the region, with nearly two million in the last seven days.