BEIJING — The number of new coronavirus cases in an outbreak in China’s northeast tripled Sunday and authorities stepped up anti-disease controls by suspending bus service to Shanghai and ordering residents of another city to stay at home.

The case numbers in China’s latest surge of infections are low compared with some other countries. But authorities are enforcing a “zero tolerance” strategy that temporarily shuts down cities to isolate every infected person despite a rising economic cost.

The government reported 1,938 new cases on China’s mainland in the 24 hours through midnight Saturday, more than triple the previous day’s total.

About three-quarters, or 1,412 cases, were in Jilin province in the northeast, where access to the industrial metropolis of Changchun was suspended on Friday and families were told to stay home after a spate of infections.

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

The territory’s leader, Chief Executive Carrie Lam, warned Saturday the peak of the latest infection surge might not be past yet.

China, where the first coronavirus cases were detected in late 2019 in the central city of Wuhan, has reported a total of 4,636 deaths on the mainland since the pandemic started out of 115,466 confirmed cases.

On Sunday, 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 center adjacent to Hong Kong.

Authorities in Jilin are stepping up anti-disease measures after concluding their earlier response was inadequate, according to Zhang Yan, deputy director of the provincial Health Commission.

“The emergency response mechanism in some areas is not sound enough,” Zhang said at a news conference, according to a transcript released by the government.

In Shanghai, China’s most populous city with 24 million people, the number of cases in the latest surge rose by 15 to 432.

The city government called on the public not to leave unless necessary. It said inter-city bus service would be suspended starting on Sunday.

“Those who come or return to Shanghai must have a negative nucleic acid test report within 48 hours before arrival,” said a city health agency statement.

Also Sunday, some residents of Cangzhou, south of Beijing, were told to stay home after nine cases were reported, according to a government notice. It wasn’t clear how many of its 7.3 million people were affected.