TAIPEI, Taiwan — Chinese authorities reported 1,337 locally transmitted cases of COVID-19 across dozens of mainland cities Monday as the fast-spreading variant commonly known as “stealth omicron” fuels China’s biggest outbreak in two years.

The vast majority of the new cases — 895 — were in far northeastern Jilin province, where the COVID-19 task force effectively banned movement throughout the province. People can leave the province or travel from one city to another only with permission from the police, according to the government notice.

The surge is infecting people in cities ranging from Shenzhen to Qingdao on the coast, to Xingtai in the north and the numbers have crept steadily higher since early March. While the mainland’s numbers are small relative to numbers reported in Europe or in the U.S., or even the city of Hong Kong, which had reported 32,000 cases Sunday, they are the highest since the first big outbreak of COVID-19 in the central city of Wuhan in early 2020.

China has seen very few infections since its strict Wuhan lockdown as the government held fast to its zero-tolerance strategy, which is focused on stopping transmission of the coronavirus as fast as possible, by relying on strict lockdowns and mandatory quarantines for anyone who has come into contact with a positive case.

The government has indicated it will continue to stick to its strict strategy of stopping transmission for the time being.

On Sunday, officials locked down the southern city of Shenzhen which has 17.5 million people and is a major tech and finance hub that neighbors Hong Kong.

On Monday, Zhang Wenhong, a prominent infectious disease expert at a hospital affiliated with Shanghai’s Fudan University noted in an essay for China’s business outlet Caixin, that the numbers for the mainland were still in the beginning stages of an “exponential rise.” Shanghai confirmed 41 new cases on Monday.

The city has recorded 713 cases in March, of which 632 are asymptomatic cases. China counts positive and asymptomatic cases separately in its national numbers.

Signs of normal life in Shanghai are abating, as schools switched to remote learning and office buildings closed. Shanghai has primarily relied on locking down single buildings instead of the whole city.

Yimeng Li, a 28-year-old Shanghai resident, said she’s on high alert because of the possibility of suddenly being quarantined. Some of her colleagues have been absent because they’ve been required to quarantine at home.

“Every day when I go to work, I worry that if our office building will suddenly be locked down then I won’t be able to get home, so I have bought a sleeping bag and stored some fast food in the office in advance, just in case,” Li said.

In Beijing, which reported six cases on Monday, multiple residential and commercial buildings were sealed off over the weekend.

City residents said they were willing to follow the zero-tolerance policies despite any personal impact.

“I think only when the epidemic is totally wiped out can we ease up,” said Tong Xin, 38, a shop owner in the Silk Market in Beijing.

Much of the current outbreak is being driven the variant commonly known as “stealth omicron,” or the B.A.2 lineage of the omicron variant, Zhang noted. Early research suggests it spreads faster than the original omicron, which itself spread faster than the original virus and other variants.

“But if our country opens up quickly now, it will cause a large number of infections in people in a short period of time,” Zhang wrote on Monday. “No matter how low the death rate is, it will still cause a run on medical resources and a short term shock to social life, causing irreparable harm to families and society.”