As 15 provincial-level regions have reported locally transmitted infections in the past week, Chinese health authorities have urged rapid response and strict implementation of the country's virus control strategies to curb the COVID-19 spread.

Wu Liangyou, deputy director of the National Health Commission's Bureau of Disease Control and Prevention, said on Saturday that Delta and Omicron are the main variants in China.

The country reported 93 local confirmed infections on Friday, including 32 in the Inner Mongolia autonomous region and 30 in Guangdong province.

Wu said that daily infections in the Inner Mongolia remain high, but the risk of the virus further spreading has come down.

However, infection clusters in several regions, including Guangdong and Yunnan provinces, and Guangxi Zhuang autonomous region are still developing and will likely transmit further.

Wu said China's virus control approaches are effective against the Omicron variant — the dominant strain globally, and the key to contain its spread is to fully implement required measures.

"The commission is guiding local governments to speed up nucleic acid screening, epidemiological investigations and management of high-risk groups," he said.

As the spring semester for schools has begun, Liu Peijun, an official with the Ministry of Education, said precaution against the COVID-19 on campus should be strengthened.

He said schools at medium- and high-risk regions are required to postpone opening and their students should delay returning until the risk of the virus' local spread is deemed low.

As of Saturday, primary and middle high schools in 25 provincial-level regions across the country have opened for spring semester, and more than 50 out of 75 centrally administered universities have started offline classes, according to Liu.

According to the commission, China had fully vaccinated over 1.23 billion people as of Friday. Nearly 555 million people had received a booster shot.