CHINA is at "very high risk" of a second deadly coronavirus wave, officials warned after a fresh outbreak in Beijing linked to a wholesale food market.
Police set up checkpoints and locked down 21 neighbourhoods as dozens more people tested positive - all workers or visitors at Xinfadi market.
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The outbreak emerged just as European nations were opening their borders to tourists for the first time in months.
In total, officials in the Chinese capital reported 79 locally transmitted cases in the past four days, following more than 50 days with zero cases.
Another 36 people tested positive in Beijing on Sunday, following 36 on Saturday, six on Friday and one on Thursday.
Tens of thousands of residents living near Xinfadi have been told to go for testing at a sports stadium and local health centres in an effort to halt the spread.
China's Vice Premier Sun Chunlan warned the risk of the Beijing epidemic spreading is "very high" and urged city authorities to impose the "strictest" measures to curb it.
KNOCK-KNOCK OPERATION
Three districts of southwest Beijing have now entered "emergency wartime mode", with 24-hour security checkpoints, schools closed and temperature checks reinstated at shops and offices.
Some districts sent officials to residential buildings in a "knock-knock" operation to identify people who had visited Xinfadi or been in contact with people who had.
"The risk of the epidemic spreading is very high, so we should take resolute and decisive measures," Xu Hejiang, spokesman for the Beijing city government, told a news conference.
The outbreak has been traced to the sprawling Xinfadi site, a giant complex of warehouses and trading spaces the size of 160 football pitches.
The meat, fish and vegetable wholesale market is more than 20 times larger than the Wuhan wet market where the global Covid-19 pandemic is thought to have originated.
It supplies around 80 per cent of fresh produce to Beijing's population of 21 million.
Local reports claimed coronavirus was found on chopping boards used to slice imported salmon - prompting supermarkets to pull fish products from shelves.
The general manager on Xinfadi was dismissed as police shut the market down in the early hours of Saturday and began testing workers.
One vegetable wholesaler told Reuters he has been quarantined for 14 days at a hotel even though his test was negative.
Other new coronavirus cases have been detected in Liaoning, Hebei and Sichuan provinces - all confirmed or suspected to be linked to the outbreak in Beijing.
Authorities in other regions were told to warn residents against travel to Beijing and to monitor those who had just come back.
Health chiefs are investigating if the virus came in from overseas after China claimed it had virtually eradicated the disease with tough lockdown measures.
One government epidemiologist said DNA sequencing of the virus showed the Xinfadi outbreak could have come from Europe.
The World Health Organization said it was informed of the outbreak it "understands that genetic sequences will be released as soon as possible once further laboratory analyses are completed."
EUROPE REOPENS
Meanwhile a number of European countries continued to lift the painful lockdown measures imposed in March.
Greece is now allowing travellers from nations deemed low-risk, and today it opened its borders to all EU residents.
Germany, Belgium, France and Austria are following suit tomorrow
And Spain said it will reopen its borders to tourists on June 21, ten days ahead of schedule - although Brits are banned until at least July 10.
But there have been two new outbreaks in Rome, with 109 cases and five deaths at a hospital and 15 infections at a building inhabited by squatters.
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"It means the virus hasn't lost its infectiousness, it isn't weakening. We shouldn't let down our guard," said WHO deputy director Ranieri Guerra.
Egypt is also set to welcome back tourists to beach resorts in July, and Peru's Machu Picchu is to reopen next month with reduced visitor numbers.
This week the English Premier League makes its long-awaited return with games played in empty stadiums after an enforced three month hiatus.