Northeast China's Heilongjiang province detected 21 new locally transmitted confirmed cases of COVID-19 and 16 asymptomatic carriers on Thursday, the provincial health commission said on Friday.

Data from the commission showed all the cases were found in Suihua city's Wangkui county and the provincial capital city Harbin, the two major affected areas in the recent outbreak.

"To ensure the safety and health of villagers who are in central quarantine after returning home, comprehensive disinfection efforts starting on Monday have been conducted in the worst-hit villages of Huiqi township in Wangkui," Dong Shuangqing, deputy Party secretary of the county, said at a news conference on Friday. "All the livestock have been transferred to safe places before the disinfection."

He added that staff members from evaluation institutions and centers for disease control and prevention would take random samples to evaluate the effect of disinfection efforts.

As of Thursday, the province had reported 554 confirmed cases and 558 asymptomatic carriers since Jan 10.

A total of 59 coronavirus patients have been discharged from the hospitals. Among 495 patients receiving treatment in hospitals, 27 are in serious condition, the commission said.

Neighboring Jilin province on Thursday reported 13 confirmed cases and seven asymptomatic carriers, according to the provincial health commission.

As of Thursday, the province had reported 316 confirmed cases and 87 asymptomatic carriers in the recent outbreak.

A total of 10 coronavirus patients have been discharged from hospitals. Among 305 patients receiving treatment in hospitals, 38 are in serious condition, the commission said.

A residential community in Changchun has been downgraded from a medium-risk area for COVID-19 to a a low-risk one starting from Thursday afternoon, officials said at a news conference on Thursday.

As of Thursday, all regions in downtown Changchun are at low risk.