BEIJING (AP) — China has placed millions of its citizens under renewed lockdown following fresh outbreaks of COVID-19, authorities reported Tuesday, as the government persists in its hard-line policy on containing the virus.

The measures affected about half of the six million residents of the port city of Dalian, along with an undisclosed number in Chengde and Shijiazhuang in Hebei province, both around three hours from the capital Beijing.

Dalian’s lockdown was due to last five days, although authorities have in past extended restrictions depending on the number of new cases.

Beijing has been relatively unaffected thus far, although travel in and out of the capital has been discouraged and residents are subject to testing on an almost daily basis.

Partial lockdowns have also been imposed on cities such as Chengdu in the southwest, Shenyang in the northeast and Jishui in the southeast.

Such measures are mandated under China’s “zero-COVID” policy, which contrasts starkly with moves by other nations to coexist with the virus through gradual easing of restrictions, vaccinations, improved therapeutics and voluntary isolation.

China has largely kept its borders closed to foreign visitors, while requiring those who do come to submit to more than a week of quarantine in hotels where sanitary conditions are often poor. Masking and regular testing are also standard and anyone found to have been in close contact with a person confirmed to have the virus is forcibly transported to field hospitals.

The World Health Organization has called China’s policy unsustainable and on Monday, a Chinese think tank issued a rare public disagreement with the ruling Communist Party, saying the curbs that have shut down cities and disrupted trade, travel and industry must change to prevent an “economic stall.”

The Anbound Research Center gave no details of possible changes but said President Xi Jinping’s government needs to focus on shoring up sinking growth. It noted the United States, Europe and Japan are recovering economically after easing anti-disease curbs.

“Preventing the risk of economic stall should be the priority task,” the think tank said in a report titled, “It’s Time for China to Adjust Its Virus Control and Prevention Policies.”

Previous lockdowns have seen tens of millions confined to their homes, sometimes for weeks. A strict lockdown in the largest city and commercial hub of Shanghai earlier this year led to protests online and in person over lack of food and medical services.

China on Tuesday reported 1,717 cases of local transmission, 52 of them in Liaoning province where Dalian is located. Most of the cases were reported in Sichuan province, whose capital is Chengdu, and the vast majority were asymptomatic.