China's financial hub Shanghai reported over 27,000 coronavirus cases on Thursday, setting a new record a day after President Xi Jinping said that the country must continue with its strict "dynamic COVID clearance" policy and pandemic control measures.

Shanghai is battling China's worst COVID-19 outbreak since the virus first emerged in Wuhan in late 2019, with the city's 25 million residents remaining largely under lockdown, though restrictions were partially eased in some areas this week.

Raising hopes for a shift in policy, on Wednesday the Chinese Center for Disease Control and Prevention (CDC) published a guide on home quarantining on its social media.

Under China's tough rules, even people without symptoms must go into quarantine at centralised facilities, where many people have complained about poor conditions.

The CDC's guide on quarantine at home - in a well-ventilated room stocked with masks, sanitizer and other gear - raised hopes that the rule for quarantine at state facilities might be relaxed.

However, when asked by a social media user in an online comments section about who might be eligible for home quarantine, the CDC referred to the old rules.

Shanghai authorities also gave no hint of any change in approach during a Thursday briefing.

On Thursday, Shanghai reported a record 2,573 symptomatic cases for the previous day, up from 1,189 a day earlier, while asymptomatic cases reached 25,146, up from 25,141.

A city official said that cases continued to rise despite the lockdown in part because of a backlog of test results and because of ongoing transmission among family members.

On Wednesday, Xi said that China must stick to its strict "dynamic COVID clearance" policy while the global pandemic remains very serious, promising those enduring lockdowns that persistence will win out in the end.

Speaking during a visit to south China's Hainan island, Xi indicated there would be no immediate change of approach in pandemic control measures, saying that the country must stick to its approach, which has all but shut China's borders to international travel, and not relax prevention measures.

China's zero-COVID policy has been increasingly challenged by the fast-spreading Omicron variant, putting millions of people under various forms of lockdown and disrupting supply chains while other countries have thrown off restrictions even though the virus is still spreading.

An April 7 study by Gavekal Dragonomics found that 87 of China's 100 largest cities by GDP have imposed some form of quarantine curbs.

On Thursday, authorities in the coronvirus-hit northeastern province of Jilin said they had stamped out local spread of COVID-19 after battling to bring cases down since mid-March.

But the southern tech hub of Shenzhen appeared to be seeing a resurgence after quashing its own outbreak last month. On Thursday, authorities reported 21 new infections, including 8 with symptoms and 13 without, its highest total since March 21.