Affected by the outbreaks, many cities have postponed the start of the new semester, which usually starts on Sept 1, including Harbin, Tianjin and Dalian. Most of the schools will temporarily provide online classes for students before the schools open.

"After the long summer vacation, I'm really missing my teachers and classmates, and now we still can't get together," said Liu Yingjin, a 9-year-old pupil from Qunli Experimental Primary School in Harbin, Heilongjiang province.

Yingjin participated in a flag-raising ceremony online on Thursday.

A dance training center in Futian district of Shenzhen, Guangdong province, is under legal investigation for its possible involvement in a cluster of COVID-19 infections, local authorities said.

The Huaxing Dance Art Center has reported 28 positive cases as of 6 pm on Wednesday, according to the district's headquarters for epidemic prevention and control.

Shenzhen reported 62 positive cases on Wednesday, with 26 of them connected with the dance center, the city's health authorities said.

Tibet's seven prefecture-level cities have basically realized zero COVID-19 status at the community level, authorities said at a news conference on Thursday afternoon.

"The region has been making solid progress in its battle against the latest COVID-19 outbreak," Chodar, deputy secretary-general of the regional government, said at the conference.

Zhou Huiying in Harbin and Palden Nyima in Lhasa contributed to this story.