The National Health Commission said seven of the new cases were local infections in Yunnan province, where a Covid-19 cluster has emerged in the city of Ruili bordering Myanmar.

Genetic analysis of cases in Ruili suggests they stemmed from viruses imported from Myanmar and are not related to other recent localised outbreaks in China, state media reported, citing a press briefing.

Ruili is a key transit point for Yunnan province, which has struggled to monitor its rugged 4,000km border with Laos, Myanmar and Vietnam for illegal immigration amid a wave of unauthorised crossings last year by people seeking a haven from the pandemic.

The city has imposed home quarantine, exit restrictions and mass testing. By Saturday it had identified 3,650 close contacts and secondary contacts of cases, state media reported.

The other 19 new infections in mainland China were imported, the National Health Commission said.

The number of new asymptomatic cases, which China does not classify as confirmed cases, rose to 24 from 20.

Confirmed Covid-19 cases in mainland China now stand at 90,252, with the death toll unchanged at 4,636.

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