Europe is entering a "tricky moment" with the new school year, the World Health Organization has said.

While classrooms have not played a major role in spreading coronavirus, there is growing evidence of young people infecting others at social gatherings, WHO regional director for Europe Hans Kluge told a news briefing.

"The younger people are not necessarily going to die from it but it's a tornado with a long tail," he said.

"At one stage, younger people particularly with the winter coming, will be in closer contact with the elder population."