China's latest Covid-19 outbreak has forced the capital Beijing to delay its annual marathon race and step up other curbs, as the sprawling city and neighbouring Hebei province go into high gear in their preparations for the 2022 Winter Olympics Games.

China reported 35 new domestically transmitted cases for Sunday, official data showed. Beijing accounted for 14 of the 168 cases reported between Oct 17-24, Reuters reported.

National health officials warned on Sunday that the latest cluster, caused by the highly transmissible Delta variant and involving many carriers who recently travelled across some provinces, is increasingly likely to expand further.

Beijing has banned entry of people from other cities with cases, and closed indoor venues such as some chess and card parlours, even in districts without infections.