Nov. 20: The World Health Organization (WHO) is "very worried" about the spread of Covid-19 within Europe as the continent battles a fresh wave of infections.
Speaking to the BBC, regional director Dr Hans Kluge warned that some 500,000 deaths could be recorded by March unless urgent action is taken.
Dr Kluge said introducing measures like mask-wearing could immediately help.
The warning comes as several nations report record-high infection rates and introduce full and partial lockdowns.
Dr Kluge said factors like the winter season, insufficient vaccine coverage and the regional dominance of the more transmissible Delta variant were behind the spread. He called for increased vaccine uptake and the implementation of basic public health measures and new medical treatments to help fight the rise.
"Covid-19 has become once again the number one cause of mortality in our region," he told the BBC, adding "we know what needs to be done" in order to fight the disease.
Dr Kluge said mandatory vaccination measures should be seen as a "last resort" but that it would be "very timely" to have a "legal and societal debate" about the issue.
"Before that, there are other means like the Covid pass," he said, adding that this is "not a restriction of liberty, rather it is a tool to keep our individual freedom."
Austria on Friday became the first European country to announce that Covid-19 vaccination would become a legal requirement. The new rules are set to come into force in February.
The announcement alongside that of a new national lockdown was made in response to record case numbers and low vaccination levels.
Many other European countries are also imposing new measures as cases arise.
Countries including the Czech Republic and Slovakia have also announced fresh restrictions on unvaccinated people as record infection rates are recorded across the continent.
Overnight, violent rioting erupted in Rotterdam in the Netherlands over new Covid-19 measures. Hundreds of protesters had gathered to show their anger at government plans for more restrictions, and a ban on fireworks on New Year's Eve.
German Health Minister Jens Spahn has described the situation there as a "national emergency" and refused to rule another national lockdown out.
The UK recorded 44,242 new coronavirus cases on Friday.
The government has consistently said it has no plans for another lockdown but has said it could bring in extra Covid measures in England to protect the NHS - known as Plan B - which include mandatory Covid passports for some indoor venues, compulsory face coverings in certain indoor settings and advice to work from home.