Discontent is deepening across Shanghai, China’s largest and wealthiest city, now several weeks into a rigid lockdown aimed at crushing a Covid outbreak that is straining the nerves and affecting livelihoods of its 25 million residents and eroding the public’s trust in authorities.

The effects that have played out in recent weeks—food shortages, lack of access to medical care, overcrowded quarantine centers and infants separated from their parents—have frayed nerves across a city that has long prided itself as a pragmatic financial hub at the forefront of China’s decadeslong shift to a market economy.

“I’ve lost confidence in this government,” said one 36-year-old Shanghai native surnamed Chen, who declined to provide his given name because it remains risky to openly criticize political leaders. “Only during a crisis can you make a proper evaluation of the government’s performance.”

Mr. Chen, who has been confined at home for more than a month, said he hasn’t been able to feed his family of four on the government-supplied rations of vegetables and milk. While he has managed to order some groceries online, soaring prices and scarce supplies of bread and other essentials risk draining his savings as the lockdown drags on, he said.

“We’ve waited patiently for the lockdown to get lifted. When will this end?” he said.

Shanghai eased rules in some neighborhoods this week, but most residents remain confined to their homes. Some expressed worries about food and said they are increasingly disillusioned by the prospect of an open-ended Covid lockdown.

Among more than two dozen residents who spoke from lockdown, some said they are reaching a breaking point more than two years into the pandemic. Some are considering leaving the country for good.

“The damage has been done,” said Liu Yun, a 34-year-old Shanghai native and technology entrepreneur who said he has begun contemplating emigrating to Singapore while confined at home with his wife and two children. “More elites will start re-evaluating their relationship with the city and this country.”

Even those who aren’t considering leaving said they expect some economic and psychological scars to endure, along with resentment toward Beijing. China has stuck to a zero-Covid policy under Chinese leader Xi Jinping,

who is widely expected this fall to extend his rule for at least another five years.

Eighty-seven of China’s biggest 100 cities, from Changchun in the country’s far northeast to its southern metropolis of Guangzhou, collectively accounting for more than half of China’s population and overall economic output, have imposed restrictions on movements and activities because of the current outbreak, according to an estimate by Gavekal Dragonomics, a research firm. On Friday, Xi’an, which earlier this year emerged from a monthlong lockdown, tightened restrictions again.

Residents lined up for Covid tests in a compound in Shanghai this week.

Photo: liu jin/Agence France-Presse/Getty Images

Few cities in China have the economic and political importance of Shanghai, which for most of the past century has been a base of prosperity at the forefront of the country’s engagement with the world. Shanghai has served as a laboratory for many of China’s most important market reforms. It is home to the world’s largest container port, the country’s main stock exchange and many of its leading scholars, writers and artists.

The city has been a crucial steppingstone for generations of China’s leaders, including Mr. Xi, who was appointed the city’s top party official in 2007.

Shanghai earlier had a more lenient Covid strategy, using targeted lockdowns for affected residences, but tightened and extended restrictions amid a visit by

Sun Chunlan, a vice premier, beginning April 2. Residents see the change as a sign Beijing demanded full compliance with China’s zero-Covid policy, which Mr. Xi has touted.

A spokesperson for the Shanghai government didn’t respond to a request for comment.

Even as Covid cases spread in the city this spring, authorities insisted that a citywide lockdown wouldn’t be necessary—right up until the day before the abrupt March 27 announcement of mass lockdown measures that caught tens of millions of residents unprepared.

That initial lockdown was set to last four days for the eastern half of the city, then four days for the western half. With case counts still soaring to new highs, however, authorities then said the lockdown would be extended indefinitely. Many of those confined to their homes because of potential contact with Covid cases before the citywide lockdown have already been kept at home for more than a month, with no clear prospect of release soon.

Residents said they worry that even after the citywide restrictions are lifted, the Omicron variant’s transmissibility means sudden lockdowns and tough tactics could return at any time, casting a cloud of uncertainty that could last for years.

Since the broad lockdowns began in late March, food shortages have spread as pandemic measures upended supply chains, leaving some reliant on bartering and the goodwill of neighbors to survive. Some patients with non-Covid medical needs have been left to fend for themselves, while many have resisted being sent to the city’s chaotic and in some cases unhygienic makeshift quarantine centers.

Shanghai on Thursday reported a record 27,000 new daily infections for the prior day, bringing the city’s total official caseload since March 1 to more than 220,000 so far. While no deaths have been reported by authorities, at least three large elderly care hospitals have been overwhelmed by Covid outbreaks, resulting in patient deaths.

Authorities have been swift to censor people’s complaints and what they call rumors online. On March 22, two men who shared information about Shanghai’s coming lockdown were investigated by the police on suspicions of “spreading fabricated information.” As the lockdown continues, more people are venting frustration at the Covid restrictions, saying they are harming people’s livelihoods and straining medical resources, despite potential repercussions.

In a viral online post, one Shanghai resident complained that the endurance of residents had “reached its limit,” listing a litany of tragedies and grievances. “Are there officials who still listen to the people?” wrote the person, who identified herself only as An Ordinary Citizen. “How much more do we have to pay in exchange for truly putting people first?”

The post was blocked on Thursday for a few hours before being restored that evening. The person didn’t respond to a request for comment.

Community workers delivered food rations on Tuesday.

Photo: alex plavevski/epa/Shutterstock

Frank Tsai, a longtime Shanghai resident who hosts business and cultural events through his company China Crossroads, initially supported the country’s strict Covid measures, but said he was shocked by the food and supply bottlenecks in Shanghai, which is widely regarded as one of China’s most progressive and best-managed cities.

“This regime from its very founding was built on the elimination of material anxiety, so it’s ironic that food insecurity is happening in Shanghai of all places,” he said.

People must “firmly hold on to its pandemic policy without wavering,” China’s state-run Xinhua News Agency said Thursday in an editorial, calling on the public to “look at the big picture” despite the hardships. “Persistence is victory,” Mr. Xi was quoted saying.

The People’s Daily, the Communist Party organ, implored citizens to “grit their teeth” and put their faith in government officials.

Some expatriates said the current lockdown is the final straw after several years in which they felt China was turning increasingly inward. “We are at a critical point. People are really fed up,” said Bettina Schoen-Behanzin, vice president of the European Union Chamber of Commerce in China.

Mr. Liu, the technology entrepreneur, was first confined to his home with his wife and two children on March 14, when the entrance to his residential compound was abruptly sealed after several neighbors were identified as “close contacts” with infected individuals. Later, the stringent citywide lockdowns began.

Li Bing said he worried about what would happen to his cats if he tests positive.

Photo: Li Bing

Mr. Liu’s social-media feed became filled with videos and messages of physical conflicts between residents and health workers tasked with keeping people at home, making him more anxious and pessimistic.

“I’m afraid that this fight against the pandemic will evolve into some kind of social movement, where people at the bottom of the society end up hurting each other,” said Mr. Liu. “That’s terrifying.”

Mr. Liu said he also worries about the roughly 200 employees at the company he founded 10 years ago, a business-to-business e-commerce platform, many of whom are struggling to get enough food during the lockdown. His company, too, is struggling from waning demand that he attributes in part to the country’s lockdowns.

Li Bing, a 33-year-old employee at a different technology company, said he felt emotionally weighed down after reading numerous online pleas from residents struggling to get enough food and medical help. Last week, a video showing a pandemic prevention worker in a hazmat suit beating a corgi to death after its owners were sent to a centralized quarantine center sparked online fury.

“What would happen to my cats? Would they be beaten to death?” said Mr. Li, a native of Xi’an who has lived in Shanghai for six years with his girlfriend and two cats. He said the prospect of testing positive for Covid has stirred his anxiety and made him more eager to leave China than ever.

“We have witnessed so many humanitarian disasters already,” said Mr. Li. “I simply want to live as a normal person, with dignity.”

A Shanghai resident was tested for Covid last weekend.

Photo: Qilai Shen/Bloomberg News

Write to Stella Yifan Xie at stella.xie@wsj.com and Natasha Khan at natasha.khan@wsj.com