The Inner Mongolia autonomous region reported 15 locally-transmitted active COVID-19 cases and 20 asymptomatic carriers on Thursday, the region's Health Commission said on Friday.

All the asymptomatic cases and 11 of the confirmed active ones were found in Xiliin Gol League. Four confirmed cases were found in Chifeng city, the commission said.

This round of new local infections started in the region a week ago. It has become a hot spot for COVID-19 on the Chinese mainland, which on Wednesday reported 30 locally-transmitted confirmed cases, 15 of which were in Inner Mongolia, the National Health Commission said on Friday.

As of Thursday, the region had a total of 148 confirmed cases and 256 asymptomatic ones, with Xiliin Gol League reporting the most in both categories — 128 confirmed patients and 248 asymptomatic cases. All were found in the league's border city of Ereenhot, officials said.

All the patients are under medical treatment and observation at designated and makeshift hospitals.

"A new makeshift hospital that was constructed in the past several days began admitting patients on Thursday morning," said Zhang Yongzhi, the city's deputy mayor, adding that the facility has 468 beds for patients.

The city has carried out seven rounds of mass nucleic acid testing for key areas. A total of 15 residential communities in Ereenhot are listed as lockdown zones, increasing the total to 82 as of Thursday, he said.

The lockdown zones are compounds with reports of COVID-19 infections over the past seven days. Residents are subject to seven days of lockdown.