Beijing's most populous district has urged residents to stay at home, extending a request from the weekend as the city's COVID-19 case numbers rise.
Many businesses in Beijing have shut and schools in the area have shifted classes online.
Nationally, new case numbers held steady on Sunday, near April peaks, as China battles outbreaks in cities across the country - from Zhengzhou in central Henan province to Guangzhou in the south and Chongqing in the southwest.
China is trying to ease the impact of containment measures that drag on the economy and frustrate residents fed up with lockdowns, quarantine and other disruptions as it reiterates its commitment to its zero-COVID approach.
On Sunday, Beijing city officials urged residents of the sprawling Chaoyang district - home to almost 3.5 million people as well as embassies and office towers - to stay home on Monday.
"The number of cases discovered outside quarantine is increasing rapidly at present and there are hidden transmission risks from multiple places," Liu Xiaofeng, deputy director of the Beijing Center for Disease Prevention and Control, told a media briefing.
"The pressure on Beijing has further increased."
The Chinese capital reported 621 new infections for Saturday, up from 515 a day earlier, and had added a further 516 new infections on Sunday afternoon.
Authorities said an 87-year-old Beijing man became the nation's first official COVID-19 fatality since May 26, raising China's coronavirus death toll to 5,227.
Many Beijing residents stocked up on food at the weekend, with some delivery services experiencing delays.
Parents at international schools in the Chaoyang district were told classes would be online for the coming week.
"As COVID-19 has spread in multiple places and with complex transmission chains, schools in Chaoyang district will be moving to online learning," one such notice said.
Hairdressers in neighbouring Dongcheng district were also told to shut.
On Sunday, China reported 24,435 new COVID-19 infections for November 19, down slightly from 24,473 a day earlier but near highs clocked in April when Shanghai, China's largest city, was in the midst of an outbreak and grinding two-month lockdown.
While official infection tallies are low by global standards, China tries to stamp out every infection chain, making it an outlier almost three years into the pandemic.
Guangzhou, a hard-hit southern city of almost 19 million people, reported 8434 new locally transmitted infections, down from 8713 a day earlier.
Under a series of measures unveiled this month, Chinese health authorities have sought more targeted COVID-19 curbs, sparking investor hopes of a more significant easing as China faces its first winter battling the highly transmissible Omicron variant.
Experts warn full reopening requires a massive vaccination booster effort and a change in messaging in a country where the disease remains widely feared.