Beijing authorities have urged social organizations in the city to strictly control interprovincial meetings and training courses, after cluster infections were brought to the city by people returning from a training course.

"Online video participation is recommended," Liu Xiaofeng, deputy director of the Beijing Center for Disease Prevention and Control, said at a news conference on Wednesday.

Beijing detected eight new local COVID-19 cases from 11 am Tuesday to 11 am Wednesday.

Seven of those cases involved people testing positive for the virus after returning to Beijing from a training course organized by a company outside the capital city, said Liu, adding that the other case involved a close contact of a confirmed COVID-19 patient in Baotou, the Inner Mongolia autonomous region.

In Hubei, the COVID-19 cluster infections from the training course in its capital have raised the case total to 23 in the latest outbreak, attributed to the Omicron variant of the virus.

Wuhan reported nine new cases in the 24 hours ending at Wednesday noon, Peng Houpeng, deputy director of the Wuhan Municipal Health Commission, said at a news conference on Wednesday.

"Of the nine newly detected cases (in Wuhan), seven were trainees at a course held by a company in Wuhan from Friday to Sunday, and the other two have been found among the close contacts," he said. "The city has conducted nucleic acid testing on 722,600 residents.

"Meanwhile, relevant departments have put a total of 663 close contacts and another 3,018 secondary contacts under quarantine to detect possible patients and asymptomatic carriers ... of the virus," he said.

To reduce the risk of the virus spreading further, Peng urged residents not to leave Wuhan unless absolutely necessary. "Those who must leave are required to show negative test results no older than 48 hours," he said.

The cluster outbreak in Wuhan has also spread elsewhere. So far, Qingdao in Shandong province and Shijiazhuang in Hebei province have also reported COVID-19 positive cases related to Wuhan.

Liu Kun in Wuhan and Du Juan in Beijing contributed to this story.