The latest COVID-19 epidemic, which has affected 28 provincial-level regions, is controllable, and China will continue with its dynamic zero-COVID policy, which has proved to be effective against the highly infectious Omicron variant, the National Health Commission said on Tuesday.

Mi Feng, commission spokesman, said at a news briefing that the fast-spreading Omicron variant is the principal cause of most of the domestic outbreaks.

"With the increasing occurrence of infection clusters, the number of new cases has risen rapidly and a growing number of regions have been hit by the virus," he said. "The epidemic situation is severe and complicated."

Lei Zhenglong, deputy director of the commission's Bureau of Disease Prevention and Control, said that as of Monday, the Chinese mainland had recorded more than 15,000 local infections in 28 provincial-level regions this month, amid the fourth wave of pandemic that hit its neighbors hard.

On Monday, the Chinese mainland registered 3,507 locally transmitted infections, nearly double the figure from the previous day. About 1,650 asymptomatic infections were also reported for Monday, according to the commission.

Lei said that the outbreaks in Jilin, Shandong, Guangdong and Hebei provinces, as well as in Shanghai municipality, were still developing and some regions are seeing a rapid increase in new cases.

Nearly 90 percent of the confirmed cases on Monday occurred in the northeastern province of Jilin. However, most of them are asymptomatic or mild cases, and only six patients were in critical or severe condition in hospitals, the commission said.

Health authorities said that China's dynamic zero-COVID policy－which features a combination of targeted lockdowns, mass testing and rapid isolation－has proved effective in tackling outbreaks of Omicron.

"Local governments are accelerating screening and the transferring and quarantine of people at risk," he said, adding that the situation is controllable.

The State Council's Joint Prevention and Control Mechanism has sent working groups to at least six provinces to help local governments take more resolute and science-based virus control measures.

Lei said greater effort will be devoted to strengthening examination of imported cold chain products, improving cross-regional coordination in tracking down high-risk groups, and further promoting mass vaccinations, particularly for people over age 80.

Wu Zunyou, chief epidemiologist at the Chinese Center for Disease Control and Prevention, said on Monday that the key to China's virus control strategy is to cut transmission chains in a timely, accurate and thorough manner.

"As long as we overcome lax attitudes and stick to strict implementation of regular virus control measures, this round of the epidemic will be effectively contained in the next couple of weeks," he said.

According to the commission, China has fully vaccinated nearly 1.24 billion people, including more than 211 million people age 60 and above.

Wang Huaqing, chief immunization planning expert at the China CDC, said that the emergence of Omicron has lifted the death rate for seniors to a record high in some foreign countries.

"At present, we should not treat the COVID-19 disease as seasonal flu," he said. "Primary inoculation and booster shots are very essential for the elderly."