COPENHAGEN: The World Health Organization expressed concern Friday over a coronavirus resurgence in Europe as Britain joined France, Germany and Austria in announcing tighter mask rules and greater testing.

Europe accounts for a fifth of the world's more than 15 million infections and remains the hardest-hit region in terms of deaths, with 207,118 out of more than 630,000 globally since the virus emerged in China late last year.

The WHO's European chapter pointed to rising cases on the continent over the past two weeks, saying tighter measures may be needed to curb the spread.

Europe like other regions is struggling to balance restrictions to halt COVID-19 against the need to revive economies as people there emerge from some of the world's toughest lockdowns.

A three-year-old girl died in Belgium, becoming the country's youngest known coronavirus victim, in a further wake-up call for a continent that has recently lifted shutdowns.

"The recent resurgence in COVID-19 cases in some countries following the easing of physical distancing measures is certainly cause for concern," a WHO-Europe spokeswoman told AFP.

"If the situation demands, reintroduction of stricter, targeted measures with the full engagement of communities may be needed."

In Spain, health authorities are facing worrying outbreaks in Aragon and Catalonia, where officials have reintroduced local restrictions and urged residents in Barcelona and its suburbs to leave home only for essential trips for two weeks.

"We have to monitor what's going on, see where we need to take action and act early," said health ministry official Maria Jose Sierra. "If the important outbreaks are controlled quickly and if we manage to ensure that there are no (other) outbreaks of such magnitude, we will have a much more contained situation."