Twenty-four new locally transmitted COVID-19 cases were reported on Sunday in Shaanxi province, the provincial Health Commission said at a briefing on Monday. Twenty-one of those cases were reported in Xi'an, with two in Yan'an and one in Xianyang. 

Large-scale citywide testing has been carried out in Xi'an, it said. 

Liu Guozhong, Party secretary of Shaanxi, said in a meeting on Sunday that the first round of testing for all residents will be completed within 24 hours.

Epidemic prevention and control work in Shaanxi has reached a "critical moment", said Liu Feng, director of the Shaanxi Center for Disease Control and Prevention, at a news conference in Xi'an over the weekend. 

On Sunday, a residential area and a dormitory of Chang'an University in downtown Xi'an was designated high-risk. Another 13 areas in the downtown area of Xi'an were adjusted as medium-risk areas for COVID-19, according to the city's epidemic prevention and control headquarters.

All primary and secondary schools and kindergartens in Xi'an, suspended classes on Monday, according to the Xi'an epidemic prevention and control headquarters. Online classes began on Monday.

Thirteen other confirmed cases were reported elsewhere on the Chinese mainland, the National Health Commission said at Monday's news briefing.