China reported nearly 3,400 daily Covid-19 cases on Sunday, double the previous day, forcing lockdowns on virus hotspots as the country contends with its gravest outbreak in two years.

A nationwide surge in cases has seen authorities close schools in Shanghai and lock down several north-eastern cities, as almost 19 provinces battle clusters of the Omicron and Delta variants.

The city of Jilin has been partially locked down, with hundreds of neighbourhoods sealed up, an official announced Sunday, while Yanji, an urban area of nearly 700,000 bordering North Korea, was fully closed off.