Health authorities in Nanjing, East China's Jiangsu province, confirmed the Delta variant was detected in the recent COVID-19 outbreak in the provincial capital.
As of Tuesday morning, Nanjing reported 106 locally-transmitted cases after a group of staff members at its Lukou International Airport tested positive for the virus last Tuesday.
Ding Jie, deputy director of the Nanjing Center for Disease Control and Prevention, said at a news conference on Tuesday the Delta variant is strongly transmissible, easy to cause severe illness and can reduce the effectiveness of treatment.
"Stricter, faster and more comprehensive measures must be taken to contain the virus," she said, adding that early infections happened when airport workers cleaned aircraft cabins.
Locally-transmitted cases have been reported in eight of Nanjing's 11 districts. It has shut down long-haul bus services out of the city since Tuesday.
All taxis and vehicles used by ride-hailing services also have been banned from leaving. All passengers leaving by train or by car must present negative nucleic acid testing results taken within 48 hours.