As of 1 pm on Friday, Jilin province had reported 526 locally transmitted COVID-19 cases and 590 asymptomatic carriers in the recent outbreak, which began on March 1, officials announced.

Of the confirmed cases, 396 were found in Jilin city, 78 in Changchun, 51 in Yanbian Korean autonomous prefecture and one in Songyuan, said Zhang Yan, deputy director of the provincial health commission, at a news conference on Friday afternoon.

Of the asymptomatic carriers, 428 were identified in Jilin, 120 in Changchun, 33 in Yanbian, two in Siping and one each in the cities of Liaoyuan and Songyuan.

"Two main transmission chains have been found in the cities of Hunchun and Jilin," Zhang said. "Gene sequencing by the Chinese Center for Disease Control and Prevention indicates the Omicron variant imported from abroad."

"Of all infected people, asymptomatic cases accounted for over 52 percent, and most of the confirmed cases are showing mild symptoms," she said. "Therefore, it is difficult to detect infected people at an early stage."

She added that some people were found positive for the virus only after tests were repeated.

"Transmission in Jilin is insidious and fast, with strong contagion," Zhang said. "The outbreak occurred during the beginning of the spring semester, and the increased cross-regional movement of people further accelerated the spread."

Cluster infections have occurred in some schools and rural areas, bringing more difficulties to epidemic prevention and control efforts, she added.

Starting at 3 pm on Friday, all residential communities and villages in Changchun, 120 kilometers from Jilin, were placed under lockdown management, and residents were asked not to leave home unless necessary, according to a statement released by the city's epidemic prevention and control headquarters.

The city has suspended all public transportation services, including buses, long-haul buses and taxis.