Yangzhou, Jiangsu province, reported 54 new locally transmitted cases of COVID-19 on Tuesday, the provincial Health Commission said on Wednesday.

Since July 20, the city has registered 448 locally transmitted cases, while the provincial capital Nanjing has identified 233.

Of the 666 locally transmitted COVID-19 cases being treated in Jiangsu's designated hospitals, 23 are in serious condition and 12 are critical.

Yangzhou started its sixth round of testing on Wednesday in its downtown areas, which have a population of more than 2 million people.

Wu Zhenglong, Jiangsu's governor, said that apart from close contacts of patients, health workers continued to identify infected people, implying that some loopholes exist in the city's virus prevention and control procedures.

"The situation of the virus-control work is very severe and complex," he said at a meeting held with the Jiangsu work team of the Joint Prevention and Control Mechanism of the State Council and the governments of Jiangsu and Yangzhou, on Tuesday.

"Quarantine measures must take effect faster and more decisively," Wu said. "It is urgent to identify and quarantine all suspected cases and all close contacts of confirmed cases and secondary contacts."

He reiterated the importance of managing quarantined areas, tracing contacts and setting up more test sample collection sitess.

He said sample collection work must be organized in a way that avoids the gathering of groups, as some people have been infected at the collection sites.