Nanjing, Jiangsu province, has upgraded two communities and two villages from low-risk to medium-risk areas for COVID-19 on Wednesday morning after nine of the samples collected from staff of the Lukou International Airport tested positive for the virus on Tuesday.

Lukou community in the city's Jiangning district, where the airport is located, has been quarantined to contain the virus, according to Nanjing's COVID-19 control and prevention headquarters.

With the upgrade, the local government has suggested people not leave the city. Anyone that has to leave the city must present a negative nucleic acid test result taken within 48 hours since Wednesday.

Nanjing Drum Tower Hospital, one of the city's top hospitals, has suspended outpatient services to help contain the virus.

As of 6 pm Tuesday, nine samples collected at the airport tested positive for COVID-19, while the rest of the samples need to be checked.

Employees testing positive at the airport were mainly ground staff, including ground services and cleaning workers, according to the official WeChat account of the Nanjing government.