The latest measures, announced on Monday, came after six Omicron cases were identified in three Chinese cities within a week, reports South China Morning Post.

Changsha in central Hunan province reported two imported Omicron cases on Saturday, after one each in Tianjin and Guangzhou earlier in the week, the newspaper reported.

Meanwhile, the Chinese mainland reported 57 new locally transmitted COVID-19 cases, the National Health Commission said in its daily report on Wednesday.

Of the new local cases, 53 were reported in Shaanxi, two in Guangdong, and one each in Tianjin and Guangxi, the commission said.

There are 20 new imported cases in six provincial-level regions, according to the commission.

Two new suspected cases arriving from outside the mainland were reported in Shanghai and no new deaths from COVID-19 were reported on Tuesday, it added.

The total number of confirmed COVID-19 cases on the mainland had reached 100,544 by Tuesday, including 1,765 patients still receiving treatment, of whom seven were in severe conditions.

A total of 94,143 patients had been discharged from hospitals on the mainland, and 4,636 had died as a result of the virus.

A total of 19 asymptomatic cases were newly reported Tuesday, all arriving from outside the mainland.