A Covid outbreak first discovered in the Chinese city of Nanjing has spread to five provinces and Beijing, with state media calling it the "most extensive contagion after Wuhan".
Almost 200 people have been infected since the virus was first detected at the city's busy airport on 20 July.
All flights from Nanjing airport will be suspended until 11 August.
All 9.3 million of the city's residents, including those visiting, will be tested, said Xinhua news.
Officials believe the current outbreak is linked to the highly infectious Delta variant of the virus and has spread further due to the fact that it was detected at a busy airport.
Testing has shown that the virus has now spread to at least 13 cities including Chengdu and the capital Beijing.