ZHENGZHOU -- The central Chinese city of Zhengzhou, capital of Henan province, launched its second citywide nucleic acid testing campaign on Thursday morning, local authorities said.

According to the municipal headquarters for COVID-19 prevention and control, the city began its second round of nucleic acid testing at 9 am Thursday and will complete the sampling process at 5 pm Friday. All residents of Zhengzhou city will be tested.

On Wednesday, Zhengzhou registered 3 new locally transmitted confirmed cases of COVID-19 and 21 locally transmitted asymptomatic cases, the provincial health commission said Thursday.

Tightening epidemic prevention and control measures, the city also classified five new areas as medium-risk for COVID-19 on Wednesday.

By Wednesday afternoon, Zhengzhou had completed its first citywide nucleic acid testing campaign, testing 11.18 million residents and locating 99 confirmed or asymptomatic cases.