BEIJING, July 31 (AFP) - China's worst COVID-19 outbreak in months has spread to two more parts of the country, health authorities said on Saturday (Jul 31), including a sprawling megacity of 31 million people.

The National Health Commission reported 55 new cases in areas including Fujian province and Chongqing municipality, in addition to the four provinces and Beijing where outbreaks of the Delta variant have already been reported.

More than 200 infections nationwide have been linked to a cluster in eastern Jiangsu province, where nine cleaners at an international airport in the city of Nanjing tested positive on Jul 20.

Nanjing city authorities ordered all tourist attractions and cultural venues not to open on Saturday, prompted by the spike in domestic transmissions.

Hundreds of thousands have already been locked down in Jiangsu province, while Nanjing has tested all 9.2 million residents twice.

The tourist city of Zhangjiajie in Hunan province, where a handful of cases attended a single theatre performance, locked down all 1.5 million residents and shut all tourist attractions on Friday, according to an official notice.

In Beijing's Changping district, where two locally transmitted cases have been found, 41,000 people in nine housing communities were placed under lockdown on Thursday.

China has previously imposed the world's first virus lockdown in early 2020 as COVID-19 seeped out of Wuhan in the centre of the country.