The speed of the spread of coronavirus in Europe is "a cause for concern", a World Health Organization (WHO) expert has said.
Dr David Nabarro, a WHO special envoy on COVID-19, warned the virus "has got so many surprises in store for us".
There were angry protests that turned violent in several countries at the weekend over tougher COVID-19 restrictions brought in to curb the new surge in cases across the continent.
Watch: Rioting in Rotterdam after Dutch tighten COVID restrictions
Austria returned to a full national lockdown on Monday, while tighter restrictions have also been introduced in the Netherlands.
There were protests in both countries at the weekend, as well as in Croatia, Belgium and Switzerland.
On Monday, Dr Nabarro said: “I’m really very, very anxious about what I’m seeing right across Europe, including now in Western Europe.”
He told Sky News: “These very large numbers of cases, but also the speed with which they’re increasing, really is a cause for concern.
“I’m not surprised because this virus is just not going away.”
Dr Nabarro added: “I’m also not surprised that people are protesting because, actually, the public in so many countries are really fed up with what’s going on.”
However he indicated that restrictions were a necessity with such high infection rates.
“We’re going to have to go on, we’re going have to go on resisting this virus and we do it through making it hard for the virus to get from one person to another with face masks and also with avoiding breathing in the air breathed out by others.
“So we’ve got to keep going. And, please, everybody take it really seriously. This virus has got so many surprises in store for us.”
According to the University of Oxford research platform Our World in Data, Austria had 1,549 new confirmed cases per one million people on Sunday, with the Netherlands on 1,227, Belgium on 1,188 and Croatia on 1,106.
In the UK, there were 604 new daily cases per one million people.
On Saturday, the WHO’s regional director, Dr Hans Kluge said he was “very worried” by Europe’s COVID-19 surge and warned there could be 500,000 further deaths by March if immediate action is not taken.
In the Netherlands, Rotterdam’s mayor, Ahmed Aboutaleb, condemned “an orgy of violence” at Friday’s COVID-19 demonstrations where seven people were hurt and more than 20 were arrested.
Hundreds of people were protesting against a fresh three-week partial lockdown, plans to introduce a COVID-19 vaccine pass and a ban on New Year’s Eve fireworks.
Some protesters launched rocks and fireworks at officers and torched police cars, while Dutch police retaliated by shooting and wounding at least two people.
In Austria, about 35,000 demonstrators, many from far-right groups, marched through Vienna on Saturday to express their anger at the country’s new lockdown.
Last week, Austria became the first European country to make coronavirus jabs a legal requirement for everyone. This will come into force from next February.
Protesters threw fireworks and bottles at police officers who used pepper spray to disperse the crowds.
There were also protests in Zurich and Lausanne in Switzerland, where a COVID-19 certificate is being proposed to gain entry to public places.
Thousands of protesters gathered on Saturday in Zagreb in Croatia, where infections have risen sharply in recent weeks even though masks are mandatory in all indoor public spaces.
Professor Peter Openshaw, a member of the government’s New and Emerging Respiratory Virus Threats Advisory Group (Nervtag), said the UK can currently avoid the measures being introduced in Europe.
“The situation appears to have really been destabilised in some parts of Europe because of misinformation, particularly about vaccines,” he told BBC Breakfast on Monday.
“I think, in the UK, we had a very successful early vaccination campaign and we got very high vaccination rates, particularly amongst those who are vulnerable.
“Obviously, that means that many people have now been vaccinated some time ago and they do need the boosters in order to raise their level of immunity back up again and make sure that, as we go into the winter season and towards Christmas, that we have very high levels of immunity again within society.”
Watch: Professor on why Europe is seeing higher Covid rates than the UK