The Chinese province of Henan has ordered its nearly 100 million people to take a Covid test every two days, an unprecedented step as the country grapples with an Omicron-fuelled surge.

China has persisted with its zero-Covid policy, imposing hard lockdowns and movement restrictions on several cities even as much of the world has transitioned to living with the coronavirus.

The curbs, including stay-at-home orders in economic engine Shanghai and creeping restrictions across Beijing, have inflicted a heavy economic toll.

To avoid a similar city-wide lockdown, local governments are adopting high-frequency testing to detect cases more swiftly and potentially isolate clusters without ordering entire populations to stay indoors.

"Residents of (Henan) province and other personnel there should complete nucleic acid sampling at least once every 48 hours," according to an article posted Sunday on the local government's website.

The testing will begin in Henan's provincial capital of Zhengzhou before the end of May, authorities said, according to the report, to help with "identifying potential risks" quickly.

Residents who do not comply will have problems scanning the codes needed to enter public places or take transport, the report added.

Other provincial capitals -- such as Shijiazhuang in the northern province of Hebei -- have also rolled out similar measures, with Shijiazhuang saying it would start weekly Covid tests for its 11 million people on Monday.

Analysts have cautioned that frequent mass testing comes at a high cost to an already faltering economy.

If similar mandates are expanded to all of mainland China, it could cost between 0.9 percent and 2.3 percent of China's gross domestic product, said Nomura analysts in a report this month.

Key business hub Shanghai has been almost entirely sealed off for around two months, snarling supply chains, while China's capital Beijing has banned dining out and ordered millions to work from home.

Retail sales and factory output slumped to their lowest levels in around two years last month, reflecting the fallout from China's zero-Covid policy.