China has reported 76 new coronavirus cases, the highest daily rise since January, including 40 domestic transmissions prompting authorities to test millions in eastern Jiangsu province, AFP reports.

"Of the 40 domestic cases, 39 were from Jiangsu province and one from Liaoning," the national health commission said in a statement, adding there had been no new deaths.

Beijing has a zero-risk approach to the virus, which emerged in the central Chinese city of Wuhan in late 2019. It locks down cities and mass tests whenever small clusters appear.

Tens of thousands of people are under lockdown in Jiangsu's provincial capital Nanjing as authorities test the city's 9.2 million residents after an outbreak linked to its airport last week.