A WHO epidemiologist said she had been devastated to watch unmasked crowds singing and shouting at the Euro 2020 soccer final in London on Sunday, expressing concerns that it would spur Covid-19 transmission, including of the Delta variant.

Britain is facing a new wave of Covid-19 driven by the more transmissible variant despite having one of the world's highest vaccination rates. It plans to scrap most remaining anti-coronavirus restrictions on July 19, in a move that worries some scientists.

In unusually forthright comments from the UN health agency, which usually refrains from remarking on the policies of individual member states, its Covid-19 technical lead Maria Van Kerkhove called the sight of the more than 60,000 spectators at the match between Italy and England "devastating".

"Am I supposed to be enjoying watching transmission happening in front of my eyes?" she tweeted in the late stages of the match.

"The #COVID19 pandemic is not taking a break tonight ... #SARSCoV2 #DeltaVariant will take advantage of unvaccinated people, in crowded settings, unmasked, screaming/shouting/singing. Devastating."

A day of alcohol-fuelled festivities had begun with rowdy scenes in central London and tens of thousands made their way to the national stadium for the game, with flares being let off in railway stations and singing on trains.

British Prime Minister Boris Johnson this month defended the decision to allow more than 60,000 people to attend the final, saying it was being hosted in a "careful and controlled manner with testing of everybody who goes there". He says vaccines have created a "considerable wall of immunity".

Globally, the rate of Covid-19 infection is rising. There were over 2.6 million new cases last week, with Europe experiencing a sharp increase of 30 %, the WHO said in its latest epidemiological update.

More than 4 million people have died since the start of the pandemic.

The WHO's emergencies head Michael Ryan also urged countries last week to use extreme caution when lifting Covid-19 restrictions, so as "not to lose the gains you've made".