A northwestern Chinese province heavily dependent on tourism closed all tourist sites Monday after finding new COVID-19 cases.
Gansu province lies along the ancient Silk Road and is famed for the Dunhuang grottoes filled with Buddhist images and other religious sites.
The National Health Commission said 35 new cases of local transmission had been detected over the past 24 hours, four of them in Gansu.
Another 19 cases were found in the Inner Mongolia region, with others spread across several provinces and cities. Residents in parts of Inner Mongolia have been ordered to stay indoors.
Despite having largely stamped out cases of local infection, China maintains a zero-tolerance policy toward the pandemic, characterised by lockdowns, quarantines and compulsory testing for the virus.
The spread of the delta variant by travellers and tour groups is of particular concern ahead of the Winter Olympics in Beijing in February. Overseas spectators already are banned, and participants will have to stay in a bubble separating them from people outside.
Authorities in the capital said on Sunday people arriving from places with recent infections would need to show a negative virus test result and give regular health reports.