Beijing's education commission has ordered the closure of the capital's schools again following a new outbreak of the coronavirus in the city of 21 million people.
The commission said on its WeChat social media account that all schools would resume online teaching from tomorrow and universities should also suspend the return of students.
Residents have been urged to stop "non-essential" travel out of the Chinese capital, and outright banned people living in "medium or high risk" areas from leaving.
"Anyone leaving Beijing must have a negative reading on a nucleic acid test taken within seven days (prior to departure)," Chen Bei, deputy secretary general of Beijing's municipal government, told a press conference.
It comes after a Beijing city official warned that the Covid-19 situation there was "extremely severe".
A huge trace-and-test programme was sparked after 27 new infections were reported there from a cluster.
The coronavirus resurgence - believed to have started at the city's sprawling Xinfadi wholesale food market - has prompted alarm as China had largely brought its outbreak under control through mass testing and draconian lockdowns imposed earlier in the year.
The new cases took the number of confirmed infections in Beijing over the past five days to 106, as authorities locked down almost 30 communities in the city and tested tens of thousands of people.
China had eased much of its anti-coronavirus measures in recent months as the government all but declared victory against the disease that emerged in Wuhan late last year.
"The epidemic situation in the capital is extremely severe," Beijing city spokesman Xu Hejian warned at a press conference.
The World Health Organization had already expressed concern about the cluster, pointing to Beijing's size and connectivity.
Officials in the city said they would test stall owners and managers at all of its food markets, restaurants and government canteens.
Beijing's testing capacity has been expanded to 90,000 a day, according to state news agency Xinhua.
The capital's transport commission banned taxi and ride-hailing services from carrying passengers out of the city, Xinhua said.
All indoor sports and entertainment venues in Beijing were ordered to shut yesterday, while some other cities across China warned they would quarantine arrivals from the capital.
The National Health Commission also reported four new domestic infections in Hebei province, which surrounds the capital, and a case reported in Sichuan province was linked to the Beijing cluster.
Authorities were racing to track people from Beijing who had travelled to other parts of China, and encouraging those who visited the capital to get tested.