BEIJING (AP) — The mayor of a northeastern Chinese city on the North Korean border that had been under lockdown for more than 50 days has apologized for failures in his administration’s work amid widespread — but often disguised — dissatisfaction over the government’s heavy-handed approach to handling the pandemic.

Dandong Mayor Hao Jianjun gave no specifics, but said government work and basic services had been “unsatisfactory,” for which he offered his apologies, according to a statement issued by the city government late Monday.

It is highly unusual for a ranking Communist Party official to publicly concede errors, particularly regarding the hardline “zero-COVID” policy that has been repeatedly endorsed by top officials under President and party leader Xi Jinping.

Despite reporting only a handful of cases, Dandong had seen one of the strictest lockdowns in China, with even deliveries of food and other necessities banned, according to unofficial sources.

In his reported comments at a meeting with residents, Hao acknowledged the sacrifices made by the city’s 2.4 million citizens, along with the “complaining voices” among them over the government’s work. Dandong would now be moving into a stage of pandemic control that would be “more proactive, more active and more effective,” Hao said.

Unable to root out the source of new cases, Dandong officials took increasingly extreme measures, some of them of questionable scientific merit. That included recommending residents close their windows to prevent the virus being blown in from North Korea, even though its ability to spread through the air is extremely limited.

Authorities have also cracked down on smuggling across the Yalu River with North Korea, offering cash incentives for information on those involved. China has long held that the virus is spreading through packaging and other surfaces, despite little evidence showing that is a significant factor.

Officials at one point also transported residents of an entire apartment block to quarantine in the city of Shenyang, about 250 kilometers (150 miles) north of Dandong. Upon their release, it was discovered the positive case sparking the move had been in a resident of a neighboring building, leading to an angry confrontation between the residents and authorities.

Lengthy lockdowns have become the norm in China’s COVID-19 response, with Shanghai’s ongoing predicament gaining the most notoriety. Most of the 25 million residents of China’s largest city and key financial hub were confined to their homes or immediate neighborhoods for two months or more and hundreds of thousands continue to remain under restrictions.

The severity of the Shanghai lockdown and the apparent lack of preparation by authorities prompted confrontations at checkpoints between residents and officials, and a series of nightly sessions of banging pots and screaming from balconies. Criticisms of the government’s policy were posted online, often in formats designed to thwart censorship software.

The relaxation of measures prompted an exodus from the city and foreign business leaders say confidence in its future as an international business hub remains in question.

The response in the capital Beijing has been more nuanced, possibly for political reasons, although many students have been forced to attend class online and a major shopping and nightlife district has been shut down following the detection of 166 cases linked to a nightclub.

Testing is required daily or every other day in most districts and failure to participate can result in a person’s cell phone health condition app being flagged, barring them from public spaces.