Northeast China's Shulan City in Jilin Province has announced that it will re-impose "closed-off management" in all communities and villages after a COVID-19 infection cluster was discovered.

At a press conference on Monday, Mayor Jin Hua said the city is in a "wartime" battle against the virus and the local government will take the strictest measures to control the spread.

One new coronavirus case was confirmed in the city on May 7, and there are 13 infections registered in the city now.

A total of 290 people, who were in close contact with the patients, have been traced and are under medical observation now. 

Authorities have now ordered all public places, including sporting facilities, scenic areas, movie theaters and libraries, be temporarily closed. All residents should stay home, except under unusual circumstances. Students in their last year of middle or senior high schools will return to take classes online.

Provincial officials also adjusted the coronavirus risk level in Shulan to high on Sunday, making it the only city in China with that designation.

Local authorities said they will conduct a thorough investigation of all Shulan residents and perform contact tracing on those who were in close contact with the newly diagnosed patients.

Besides a re-imposed community lockdown, the local railway company halted nearly a dozen train services, in and out of the city, from Sunday through the end of May.

All public transportation, including buses, also suspended service starting Sunday. No taxis are also allowed to leave the city.

The local government vowed to satisfy all residents' daily needs while implementing the new restrictions.