China's northeastern port city of Dalian has started to conduct nucleic acid tests on all its citizens in the wake of new COVID-19 cases reported recently, local authorities said on Tuesday.

The city began doing the tests at noon on Tuesday. The tests will likely last for three days to cover all citizens in Dalian.

Its citizens are required not to leave the city unless necessary, and for those who do need to leave, a negative nucleic acid test result within seven days is required.

From Dec. 15 to 21, the city reported five confirmed domestically transmitted COVID-19 cases and 12 domestically transmitted asymptomatic cases.