China reported 5,280 new Covid-19 cases on Tuesday, more than double the previous day's tally and the highest daily count since the start of the pandemic.
The northeastern province of Jilin was worst hit, accounting for more than 3,000 cases, according to the National Health Commission.
Since the Coronavirus first emerged in the central city of Wuhan in late 2019, China had successfully suppressed large-scale outbreaks through its strict "zero-Covid" strategy, which involved hard lockdowns that confined huge sections of the population to their homes.
But Tuesday was the sixth day in a row that more than 1,000 new cases were recorded in the world's second-biggest economy.
At least 11 cities and counties nationwide have been locked down because of the latest surge, including the southern tech hub of Shenzhen, home to 17 million people.
Hong Kong stocks plunged by more than three per cent Tuesday, extending the previous day's tech-fuelled rout.
Dozens of domestic flights at airports in Beijing and Shanghai were cancelled Tuesday morning, flight tracking data showed.
An outbreak at Volkswagen Group factories in the Jilin city of Changchun also prompted three sites to shut Monday for at least three days, according to a spokesman.
Various other cities including Shanghai have sealed off certain neighborhoods and buildings, as authorities have sought to minimize disruption to daily life.
But health officials have warned tighter restrictions could be on the way.
Jilin's governor vowed to go all-out to "achieve community zero-Covid in a week" during an emergency meeting Monday night, state media reported.
Residents of Jilin, which is on the border with North Korea, were banned from travelling out of and around the province Monday.