Beijing reported a record number of new Covid-19 cases for its current outbreak, reviving concern that the city may face a broad lockdown as authorities seek to stamp out community spread of the virus.

The Chinese capital recorded 99 infections for Sunday, up from 61 on Saturday. While the total is still low, the spike is one of the biggest since the outbreak started, with the case tally mostly hovering around 50 a day.

The growing outbreak in Beijing underscores the challenges of China's Covid Zero approach, with the unprecedented shutdown of Shanghai providing a cautionary tale of how early mistakes could lead to rapid spread of a virus China is still trying to wipe out. The strategy has become increasingly controversial in the face of highly transmissible variants, leaving the country isolated from the rest of the world despite the harsh containment measures, even as officials look for ways to minimize the economic fallout.