A viral video showing the impact of the prolonged coronavirus lockdown on Shanghai's residents has been taken down by China's internet censors Saturday, triggering an online backlash.

About 25 million residents in Shanghai have been shut in their homes since early April, as officials rush to curb its worst ever outbreak since the beginning of the pandemic.

The city has struggled to provide fresh vegetables and other essentials to those in lockdown, while patients have reported trouble accessing regular medical care as thousands of health staff were deployed to covid testing and treatment.

The issues were chronicled in a six-minute video titled "Voice of April", which was widely shared on Weibo and WeChat -- major social media platforms in China.

Shot against a simple aerial black-and-white view of the city, the video opens with audio clips from media briefings in March where officials say Shanghai will not have a citywide lockdown.

The decision was quickly reversed by April as the highly transmissible Omicron variant led to a spike in infections.

As the camera pans across the empty streets of Shanghai, audio clips are played in chronological order showing the dire situation of residents shunted into their homes without preparation.

"We have gone to the hospital twice, but no one is there to treat us," a man whose father is ill is heard saying.

In another, a woman complains about not being allowed back home when she returned from hospital after chemotherapy.

There is also a clip of residents yelling, "Thank you, Big Whites" -- a nickname for health staff dressed in white PPE gear deployed to various nieghbourhoods.

Internet censors battled for hours Saturday to scrub the video from Weibo and Wechat, as netizens kept uploading it into different cloud services.

Shanghai's 25 million residents have been under lockdown since early April as authorities try to curb an Omicron-fuelled outbreak
Shanghai's 25 million residents have been under lockdown since early April as authorities try to curb an Omicron-fuelled outbreak AFP / Hector RETAMAL

The swift censorship of the video -- which was posted by an anonymous account -- led to an online backlash.

"The video was just presenting raw facts. There is nothing provocative!" said one commentator on Weibo.

"Its content is nothing new... But the fact of seeing that even that is censored, it bothers me," wrote another.

"Voice of April" is not accessible on any major social media platform in China as of Saturday afternoon, but it can still be viewed on Youtube.

Shanghai reported 23,504 new coronavirus cases and 12 deaths on Saturday.

While China's zero-covid strategy had kept the country relatively infection-free during the pandemic's first two years, the current wave has seen hundreds of millions of people across the country placed under some form of lockdown.

Public criticism against the government is extremely rare, but the prolonged restrictions are testing the patience of the Chinese -- with protest footage circulating on social media faster than censors can delete it.