SHANGHAI, May 21 (REUTERS) - Shanghai cautiously pushed ahead on Saturday (May 21) with plans to restore part of its transport network in a major step towards exiting a weeks-long Covid-19 lockdown, while Beijing kept up its defences in an outbreak that has persisted for a month.

Shanghai's lockdown since the beginning of April has dealt a heavy economic blow to China's most populous city, stirred debate over the sustainability of the nation's zero-Covid-19 policy and stoked fears of future lockdowns and disruptions.

Unlike the financial hub, Beijing has refrained from imposing a citywide lockdown, reporting dozens of new cases a day, versus tens of thousands in Shanghai at its peak.

Still, the curbs and endless mass testing imposed on China's capital have unsettled its economy and upended the lives of its people.

As Beijing remained in Covid-19 angst, workers in Shanghai were disinfecting subway stations and trains before planned restoration of four metro lines on Sunday.

While service will be for limited hours, it will allow residents to move between districts and meet the need for connections to railway stations and one of the city's two airports. More than 200 bus routes will also reopen.

Underlining the level of caution, Shanghai officials said commuters would be scanned for abnormally high body temperatures and would need to show negative results of polymerase chain reaction tests taken within 48 hours.

Shanghai found 868 new local cases on Friday, compared with 858 a day earlier, municipal health authorities said on Saturday, a far cry from the peak in daily caseloads last month.

No new cases were found outside quarantined areas, down from three a day earlier, health authorities added.

The city of 25 million people has gradually reopened shopping malls, convenience stores and wholesale markets and allowed more people to walk out of their homes, with community transmissions largely eliminated in recent days.

Still, Shanghai tightened stringent curbs on two of its 16 districts on Friday.

The authorities "urge enterprises to strictly implement safe production, which is their responsibility, especially in meeting some epidemic prevention and control requirements", an official from the city's emergency bureau told a news conference on Saturday.

Delta Airlines said on Friday it would resume one daily flight to Detroit from Shanghai via Seoul on Wednesday.

Drawing comparisons

Most of Beijing's recent cases have been in areas already sealed up, but the authorities remained on edge and quick to act under China's policy.

In Fengtai, a district of two million people at the centre of Beijing's counter-Covid-19 efforts, bus and metro stations have been mostly shut since Friday and residents told to stay home.

A Fengtai resident was stocking up on groceries at a nearby Carrefour on Saturday, uncertain whether restrictions would continue.

"I'm not sure if I can do more shopping over the next week or so, so I've bought a lot of stuff today and even bought some dumplings for the Dragon Boat holiday" in early June, she said, asking not to be identified.

On Friday, thousands of residents from a neighbourhood in Chaoyang, Beijing's most populous district, were moved to hotel quarantine after some cases were detected, according to state-run China Youth Daily.

Social media users on China's Twitter-like Weibo were swift to draw parallels with Shanghai, where entire residential buildings were taken to centralised quarantine facilities in response to a single positive Covid-19 case in some instances.

While unverified accounts from residents of the Nanxinyuan neighbourhood garnered thousands of comments and shares on Weibo, a related hashtag could not be searched on the platform on Saturday.