Of the 57 new cases logged by Chinese authorities, 36 were domestic infections in the capital
China reported its highest daily number of new coronavirus cases in months on Sunday with parts of Beijing still under lockdown, offering a second wave warning as more European countries prepare to open their borders for travel.
The shock resurgence in domestic infections has rattled China, where the disease emerged late last year but had largely been tamed through severe restrictions on movement that were later emulated across the globe.
It also gives a bleak insight into the difficulties the world will face in conquering Covid-19 - even as Europe prepares for the summer holiday season after an encouraging drop in contagion, with some countries set to welcome visitors from elsewhere on the continent from Monday.
Of the 57 new cases logged by Chinese authorities, 36 were domestic infections in the capital, where a large wholesale food market at the centre of the outbreak has been closed and nearby housing estates put under lockdown.
"The meat sellers have had to close. This disease is really scary," said a fruit and vegetable trader surnamed Sun at another central Beijing market, adding there were fewer customers than normal.
Others were more sanguine. "As long as you wear a face mask, it should be fine... Anyway, I have to buy food, right?" said shopper Song Weiming.
At least 429,000 people worldwide have died from the respiratory illness, nearly halfway through a year in which countless lives have been upended as the pandemic ravages the global economy.
The total number of confirmed cases has doubled to 7.7 million in slightly over a month and the disease is now spreading most rapidly in Latin America, where it is threatening healthcare systems and sparking political turmoil.
Brazil has the second-highest number of virus deaths after the United States, surpassing Britain's toll, and the Chilean health minister resigned on Saturday amid a furore over the country's true number of fatalities.
There is still no treatment for Covid-19, but pharmaceutical group AstraZeneca said it has agreed to supply an alliance of European countries with up to 400 million doses of a possible vaccine.
German government sources told AFP a vaccine could be developed by the end of the year.
Many European nations are further lifting painful lockdowns that have saved lives and forced caseloads down, but have also withered economies and caused misery for millions.
The EU has recommended that member states fully reopen their frontiers with each other on June 15, but the border reopenings have been far from harmoniously coordinated.
Some like Poland have done so already, with people from other European Union countries allowed to visit, and Germany said it would end land border checks on Monday.
Greek Prime Minister Kyriakos Mitsotakis travelled to picturesque Santorini island on Saturday to open his country's tourism season.
"Greece is ready to welcome tourists this summer by putting safety and health as our number one priority," he said in English in front of a spectacular sunset.
France has said it will gradually reopen to countries outside the borderless Schengen zone from July. French President Emmanuel Macron is set to give a speech on Sunday, in which he will detail plans to further relax virus restrictions.
But even in the much-awaited global sporting revival, there are wobbles - Australian rugby league officials postponed a top-level game on Sunday hours before kick-off due to a coronavirus scare.
The World Health Organization said this week the pandemic is accelerating in Africa, and Botswana's capital Gaborone was locked down Saturday after new cases were detected.
And in the US, which has seen the most Covid-19 deaths with over 115,000, more than a dozen states - including populous Texas and Florida - reported their highest-ever daily case totals in recent days.
The rise comes as huge anti-racism protests rage across America and the world, with many demonstrators wearing masks to protect against the spread of the virus.