China has reported 13,000 Covid cases, the most since the peak of the first pandemic wave over two years ago, as health officials say they have found a suspected new subtype of the Omicron variant in the Shanghai area, reports AFP.

Until March, China had successfully kept the daily caseload down to double or triple digits, with hard, localised lockdowns, mass testing and travel restrictions.

But cases have surged over recent weeks to thousands each day, especially in the outbreak epicentre of Shanghai, where streets were eerily empty on Sunday as 25 million people stayed in under lockdown orders.

Officials in Suzhou, a city 30 minutes west of Shanghai, have detected a mutation of the Omicron variant not found in local or international databases, state media reported.