Beijing reported 20 COVID-19 cases between Friday and Saturday and the preliminary epidemiological investigation showed that the virus has been spreading insidiously for one week, a senior official of the capital's heath authority said at a news conference.

Beijing reported 15 new locally transmitted COVID-19 cases between 10 pm Friday and 4 pm on Saturday, said Pang Xinghuo, deputy director of the Beijing Center for Disease Prevention and Control.

This round of the confirmed cases involved a wide range of people, including students, tour group for senior people and interior decoration staff. The infected people have been to a number of places.

Therefore the authority said the infection risks remains high and the number of cases is expected to rise in the following days, Pang said.

A school in Chaoyang district reported 10 cases on Friday and Saturday. The school was put under control management on Friday.

Some residential communities in Chaoyang are also under the control management.

All the drivers and tour guides of tourist companies that organized urban tours in the 14 days before Saturday have been asked to undergo nucleic acid tests and work from home before the results come out.