Beijing reported seven new locally transmitted COVID-19 cases between Monday and 3 pm Tuesday, due to an infection cluster involving people who have returned to the capital from overseas, a senior official said at a news conference on Tuesday afternoon.

The city reported three cases on Monday and four on Tuesday - one in Tongzhou district and the rest in Yanqing, according to Liu Xiaofeng, deputy director of the Beijing Center for Disease Prevention and Control.

One of the cases, living in a hotel in Yanqing, was found via mass nucleic acid testing. The patient completed 14 days of centralized quarantine outside Beijing after arriving in the country from overseas on June 15 and flew back to Beijing on July 1. The person took the test on Sunday and was confirmed of COVID-19 on Monday.

The other six infected people are all colleagues of the initial case.

In addition, Shunyi district reported two people had positive results in their nucleic acid tests on Tuesday, saying these two cases are linked to the confirmed cases from Yanqing.

"Imported cases are the biggest risk in the current epidemic control and prevention in Beijing," Liu said. "Swift action and epidemiological investigations will be taken to cut transmission."

Prior to the new cluster in Yanqing, Beijing had reported zero new local COVID-19 cases for several days after the previous cluster linked to a bar was effectively contained.