0147 GMT November 29, 2021
Speaking to the BBC, regional director Hans Kluge warned that 500,000 more deaths could be recorded by March unless urgent action is taken.
Kluge said an increase in mask wearing could immediately help.
The warning comes as several nations report record-high infection rates and introduce full and partial lockdowns.
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.
Austria on Friday became the first European country to announce that COVID-19 vaccination would become a legal requirement.
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 rise.
Countries including the Czech Republic and Slovakia have also announced fresh restrictions on unvaccinated people as record infection rates are recorded across the continent.
In Germany, Health Minister Jens Spahn described the situation as a "national emergency" and refused to rule out another national lockdown.
The UK recorded 44,242 new coronavirus cases on Friday.
The government has consistently said it has no plans for another lockdown for England.
In France, President Emmanuel Macron has made it clear he thinks high levels of vaccinations should be enough to avoid future lockdowns.
Thousands took to the streets across Europe on Saturday to protest fresh rounds of COVID restrictions.
In the Netherlands, rioters threw stones and fireworks at police, and set fire to bicycles as protests against coronavirus curbs turned violent for a second night in the country, according to Deutsche Welle.
At least 40 people were detained across three provinces.
A day earlier, at least two people were injured after police fired shots at protesters and 51 were arrested at an anti-coronavirus restrictions demonstration in the city of Rotterdam.
Around 35,000 protesters, many from far-right groups, marched through the Austrian capital Vienna.
In Northern Ireland, several hundred people opposed to vaccine passports protested outside the city hall in Belfast.
The government of Northern Ireland voted this week to introduce vaccine certificates for admission to restaurants starting December 13.
In Croatia, thousands gathered in the capital of Zagreb. Some carried flags, nationalist and religious symbols, along with banners against vaccination and what they describe as restrictions of people’s freedoms.
In Italy, 3,000 turned out in the capital’s Circus Maximus to protest against “Green Pass” certificates required at workplaces, restaurants, cinemas, theaters, sports venues and gyms, as well as for long-distance train, bus or ferry travel.
Protests were also held in several other European countries.