Bus services in the eastern port city of 24 million people have been suspended and a negative COVID-19 test is required from anyone wanting to enter.

The authorities reported 1,938 new coronavirus cases on the Chinese mainland on Sunday, more than triple the previous day's total.

Around three-quarters of those - 1,412 cases - were in Jilin province in the northeast, where entry to the industrial city of Changchun has been suspended and families told to stay at home.

Stricter measures were introduced after officials decided an earlier response was inadequate.

Zhang Yan, deputy director of the provincial health commission, said: "The emergency response mechanism in some areas is not sound enough."

In Shanghai, China's most populous city, the number of cases rose by 15 to 432.

The city government called on the public not to leave unless necessary.

Although China's infection numbers are relatively low, the authorities are enforcing a "zero tolerance" strategy to find and quarantine every infected person.

In Hong Kong, the local government reported 15,789 new daily cases, down by almost half from Saturday's total.

Its leader, chief executive Carrie Lam, warned on Saturday that the latest infection surge might not yet be past its peak.

Some residents of Cangzhou, a city of 7.3 million people south of Beijing, have also been told to stay at home after nine cases were reported, according to a government notice.

On the mainland, 831 new cases were reported in Changchun, 571 in the nearby provincial capital city of Jilin, 150 in the eastern port city of Qingdao and 60 in Shenzhen, a business centre next to Hong Kong.

Figures published earlier this week showed six million people have now died of coronavirus since the pandemic began.