COPENHAGEN -- The World Health Organization (WHO) in Europe on Thursday said it was seeing an "explosion" of coronavirus cases in the region and warned of a "tough time" ahead as mortality rates rose.

"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.

Kluge, who was wearing a mask even as he was interviewed over a webcam meeting, also said the mortality rate could be seen rising "little by little."

"It's going to be a little bit of a tough time, we need to be honest on that," he said.

In spite of the rapidly rising cases, Kluge cautioned that closing schools should be seen as a last resort, especially in light of there being "no reasons to say that schools are a main driver of the transmission."

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

While managing the COVID-19 pandemic was the immediate concern, Kluge also said there were lessons to learn in case an even more dangerous virus were to appear.

"Imagine that COVID was as easily transmitted as measles, or imagine that COVID was as lethal as Ebola... We need to take this chance to be better prepared for the future," Kluge said.