A woman is tested for the coronavirus near the central hospital in Shanghai. AFP

China's Shanghai reported 5,298 asymptomatic COVID-19 cases and 355 symptomatic cases for March 30, the city government said on its official WeChat account on Thursday.

The financial hub authorities on Thursday appealed to residents to keep cooperating with tight curbs imposed to stop COVID-19 spreading, saying they recognised their frustrations as China's most populous city entered the fourth day of a two-stage lockdown.

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That compared with 5,656 new asymptomatic cases and 326 new cases with symptoms reported a day earlier.

Shanghai on Sunday announced a two-stage lockdown of the city of 26 million people to carry out COVID-19 testing.

Health workers work along a street in Jing’an district in Shanghai. AFP

The plea for patience came as the Chinese financial hub, home to 26 million people, said its overall daily COVID caseload eased, for the first time in about two weeks, in an outbreak of the highly contagious Omicron variant that began about a month ago.

In a letter to the city's residents, the Shanghai government saying it was grateful for citizens' efforts and acknowledged their sacrifices, as it sticks with China's "dynamic clearance" approach - detecting the virus, tracing contacts and centrally quarantining all positive cases.

"Pandemic prevention and control work have brought much inconvenience to people," it said in the letter, posted to its official WeChat social media account on Thursday.

"Some of you have been in quarantine and lockdown for a long time. The city deeply appreciates everyone's understanding and cooperation."

Health workers in personal protective equipment (PPE) work at a barrier in Shanghai, China. Reuters

Shanghai is being locked down by splitting the city into two roughly along the Huangpu River, dividing the historic centre west of the river from the eastern financial and industrial district of Pudong. Authorities say this allows for staggered mass testing.

Movement curbs on residents in the eastern districts started on Monday and are set to be lifted at 05:00 local time (21:00 GMT) on Friday.

Areas west of the river will be locked down from 03:00 on the same day, though some housing compounds in western districts already directed residents to stay home from Wednesday.

Many across the city have taken to social media to vent their frustrations in lockdown, posting videos and images of crowded quarantine centres and also issuing calls for help with medical treatment and purchasing food.