Authorities in the Chinese city of Shanghai have denied rumours of a city-wide lockdown after a sixth straight increase in daily asymptomatic coronavirus cases pushed its count to record levels despite a campaign of mass testing aimed at stifling the spread.

Daily new local Covid-19 infections in Shanghai neared 1,000, but authorities vowed to stick with a “slicing and gridding” approach to screen neighbourhoods one by one, rather than shut down entirely, Reuters reported.

The lockdown rumours triggered panic buying late on Tuesday night, with slots on Alibaba's “Freshippo” delivery app running out a minute after midnight.

“Please do not believe and spread rumours,” the city government said on its Weibo microblog site.