Millions of people were confined to their homes in China as the country tried to contain its largest coronavirus outbreak in months with mass testing and travel curbs.

China reported 55 new locally transmitted coronavirus cases on Monday, as an outbreak of the fast-spreading Delta variant reached over 20 cities and more than a dozen provinces.

Local governments in major cities including Beijing have now tested millions of residents, while cordoning off residential compounds and placing close contacts under quarantine, AFP reports.

The central city of Zhuzhou in Hunan province ordered over 1.2 million residents to stay home under strict lockdown for the next three days as it rolls out a citywide testing and vaccination campaign, according to an official statement.