Residents were told to “self-quarantine or go to designated venues to quarantine” after returning to the Chinese capital from holidays.
The measure came as Egypt confirmed the first coronavirus case in Africa.
Over 1,500 people have died from the virus, which originated in Wuhan city.
The notice on Friday from Beijing’s virus prevention working group was issued as residents returned from spending the Lunar New Year in other parts of China.
The holiday was extended this year to help contain the outbreak.
More than 20 million people live in Beijing.
China’s national health commission on Saturday reported 143 new deaths, bringing the toll to 1,523. All but four of the latest victims were in hard-hit Hubei province.
A further 2,641 people have been newly confirmed as infected, bringing the national total to 66,492.
Outside mainland China, there have been more than 500 cases in 24 countries, and three deaths: one each in Hong Kong, the Philippines and Japan.
A World Health Organization (WHO)-led mission to China will start its outbreak investigation work this weekend, focusing on how the virus – officially named Covid-19 – is spreading and its severity, director Tedros Adhanom Ghebreyesus said.
The mission, including international experts, will also look at how and when more than 1,700 health workers contracted the virus.
The team consists of 12 international members and their 12 Chinese counterparts.
“Particular attention will be paid to understanding transmission of the virus, the severity of disease and the impact of ongoing response measures,” said Dr Mike Ryan, executive director of the WHO health emergencies programme.
Africa sees its first case
Egypt’s health ministry on Friday confirmed the first case of the coronavirus in Africa.
The ministry described the person as a foreigner, but did not disclose the nationality.
It said it had notified the WHO, and the patient had been placed in isolation in a hospital.
Experts had earlier warned that it may not be long before the first case was confirmed in Africa, given its increasingly close ties to China.
Chinese health workers die in the outbreak
Chinese officials say six health workers have died.
Zeng Yixin, vice minister of China’s National Health Commission, said 1,102 medical workers had been infected in Wuhan and another 400 in other parts of Hubei province.
“The duties of medical workers at the front are indeed extremely heavy; their working and resting circumstances are limited, the psychological pressures are great, and the risk of infection is high,” Mr Zeng said, as quoted by Reuters news agency.