Staff members disinfect a waiting room of Beijing Railway Station in Beijing, capital of China, June 18, 2020. (Xinhua/Chen Zhonghao)

BEIJING, June 18 -- Beijing has published a slew of measures to tighten the control of personnel flow following the emergence of several new clusters of COVID-19 infections, a security official said at a press conference Thursday.

People belonging to three categories are not allowed to leave Beijing, according to Pan Xuhong, deputy head and spokesperson of the municipal public security bureau.

The first category includes confirmed COVID-19 patients, suspected cases, close contacts, asymptomatic carriers and people with fever. The second covers those who have visited Xinfadi wholesale farm-produce market or had close contact with relevant staff since May 30. The third includes people living in medium- and high-risk areas.

Most of the new confirmed cases in Beijing were related to the Xinfadi market in the city's Fengtai District.

Other personnel should avoid unessential travels outside Beijing, Pan said, adding that a negative nucleic-acid test certificate issued within the past seven days is a must for those who really need to leave the city.

Civil aviation and railway departments have also imposed restrictions on the purchase of tickets for confirmed and suspected cases, close contacts and asymptomatic carriers in Beijing, as well as those who have been to the Xinfadi market or had close contact with relevant staff since May 30.

All interprovincial bus lines operated by Beijing's carriers will be suspended starting from June 19, Rong Jun, deputy director of the Beijing Municipal Commission of Transport, told a press conference on Thursday afternoon.

Any purchased bus tickets will be refunded, Rong added.

From June 11 to 17, Beijing reported 158 domestically transmitted COVID-19 cases.