Beihai, a coastal city in the Guangxi Zhuang autonomous region, has reported 186 asymptomatic COVID-19 infections since Tuesday, spurring temporary lockdown of its downtown region, according to local officials.

The first reported case of the latest cluster was found in Haicheng district on Tuesday and a number of cases are associated with Jingui market, the city's largest wholesale market.

Genome sequencing results show that the outbreak was triggered by the BA.2.3 subvariant of Omicron, a highly infectious strain that has a short incubation period and mostly results in symptom-free infections.

No confirmed cases have been registered in Beihai.

As of Friday morning, the city had designated 86 high-risk level areas and 70 medium-risk level areas, health officials said.

Since Wednesday, the city had imposed COVID-19 curbs on the Haicheng district and the neighboring Yinhai district, including halting entertainment and fitness venues, offline training institutions and suspending dine-in services.

All tourist attractions in the city have also been shut down.

Lan Tianli, chairman of the autonomous region, said during a conference on Thursday that the outbreak in Beihai is developing and the risk of the novel coronavirus spreading further is large.

Rigorous and rapid control measures should be rolled out to seize "the window of opportunity" to cut the virus' transmission, he added.

To ensure medical demands of people living in locked-down areas or undergoing isolation, the city designated Yinhai People's Hospital to receive them, officials said during a news conference on Friday morning.

Meanwhile, the city has arranged seven suppliers to facilitate residents in controlled areas to purchase food and other materials. It is also mulling issuing subsidies to low-income residents in locked-down regions.

Zhang Xiaofang, a supplier of chicken and duck at Jingui market, said the market was locked down on Tuesday morning.

Because most vendors like her sell products on the first floor and live on upper floors, they are now being quarantined at home.

"Healthcare workers conduct door-to-door nucleic acid tests for us every day, and there are plenty of vegetables and meat in stock," she said.

As summer is a peak tourism season for Beihai, Lan, chairman of the autonomous region, also required prompt measures to count, screen and accommodate tourists stranded in the city.

The city should also step up communication with authorities of other regions with travelers returning from Beihai to reduce the risk of the virus' spread, he added.

The mainland reported 64 confirmed, local cases and 368 asymptomatic infections on Thursday, according to the National Health Commission.

On Friday, Huaiyuan county in Anhui province said that it had detected 151 positive infections during an initial screening conducted the previous day.

The whole county has been locked down and mass testing is underway, according to the local government.