China on Sunday reported 75 new cases of COVID-19 on the mainland for July 31, up from 55 cases a day earlier, including new locally transmitted cases in eight provinces.

The wave is part of an expanding COVID-19 Delta variant outbreak in China that is becoming increasingly severe, following months of little to no locally transmitted cases.

The eastern province of Jiangsu recorded 30 new locally transmitted cases, up from 19 a day earlier, following news on Saturday that a cluster in the province's capital, Nanjing, had risen to 184 cases.

Officials on Friday said early cases of the Nanjing outbreak were linked to workers at the Nanjing Lukou International Airport, who cleaned a plane after it arrived from Russia carrying an infected passenger.

They confirmed the cases were the Delta variant of the COVID-19 virus.

There were also 12 new cases reported in central China's Henan, where the flood-stricken city of Zhengzhou reported 11 new cases as of Saturday, as well as 16 asymptomatic cases, which China does not include in official figures.

Among the 75 new cases reported across China were 22 imported from overseas, down from 25 a day earlier.

China's total number of current infections stands at 1,022 cases, with no new deaths reported. The country has reported a total of 93,005 infections since the outbreak began.

China has administered over 1.6 billion doses of COVID-19 vaccines as of July 30.