Europe remains "in the firm grip" of Covid and the death count on the continent could top 2.2 million this winter if current trends continue, the World Health Organization said Tuesday.

Some 700,000 could die in the coming months, the WHO said, as cases creep up across Europe, prompting some countries to reimpose tough restrictions.

The WHO expects "high or extreme stress in intensive care units (ICUs) in 49 out of 53 countries between now and March 1, 2022".

"Cumulative reported deaths are projected to reach over 2.2 million by spring next year," it added, up from the current 1.5 million.

Covid-19 is the leading cause of death across Europe and Central Asia, the WHO reported, citing figures from the Institute for Health Metrics and Evaluation.

The rise in Europe was being driven by a combination of the highly-contagious Delta variant, insufficient vaccination coverage and the easing of measures such as mask wearing and physical distancing, it said.

According to WHO data, Covid-related deaths increased last week to nearly 4,200 a day, doubling from 2,100 deaths a day at the end of September.

The WHO also said evidence was growing that vaccine-induced protection against infection and mild disease was declining.

"The Covid-19 situation across Europe and Central Asia is very serious. We face a challenging winter ahead," regional director for WHO Europe, Hans Kluge, said in a statement.

He called for a "vaccine plus" approach, consisting of vaccinations, social distancing, the use of face masks and hand washing.

The WHO said face masks reduce Covid incidence by 53 percent according to a recent study, and "over 160,000 deaths could be prevented (by March 1) if universal mask coverage of 95 percent was achieved".