The progress COVID-19 over the next one or two weeks will be key to assessing whether a new wave of infections has started in Nanjing and whether more cases will occur, said Dr Zhang Wenhong, Shanghai's COVID-19 expert team leader.

If no more coronavirus infection cases are reported in the next one or two weeks outside Nanjing, that means the virus is controlled in the Jiangsu city, Zhang said.

"Strict prevention and control measures have been taken in Nanjing and we should be confident about bringing the spread of the pandemic under control," he said.