Reports of new cases of COVID-19 in Qingdao, Shandong province, have caused the city to activate a plan to conduct citywide nucleic acid testing, while officials said late on Monday that the city as a whole is at low risk of community-level spread of the virus.

Cases started to appear over the weekend, and the city had reported 12 new confirmed cases, six of them asymptomatic, as of noon on Monday.

The citywide low risk level is a result of all the new reported cases being linked to Qingdao Chest Hospital, Zhang Huaqiang, deputy head of the Qingdao Disease Control and Prevention Center, said at a city news conference on Monday night.

The Loushanhou community, where the hospital is located, has been designated a medium-risk area for COVID-19 control and prevention, he said. The hospital, which was used to treat imported COVID-19 cases, was shut down on Sunday.

The city plans to complete free nucleic acid testing in five districts within the next three days, and the testing will cover the whole city of 9 million in five days, according to a notice issued by the municipal health commission. The results will be released in a timely manner, the notice said.

The outbreak comes after two months with no local virus transmissions reported in China.

The National Health Commission sent a working group on Monday to supervise epidemic prevention and control in Qingdao.

Shandong province has also been mobilizing medical resources since Sunday morning, including gathering medical staff and facilities to support the city's efforts.

As a tourist destination, Qingdao welcomed more than 4.4 million visitors from Sept 28 to Thursday, officials said.