SHANGHAI (REUTERS) - The Shanghai authorities battling an outbreak of Covid-19 have erected mesh barriers outside some residential buildings, sparking fresh public outcry over a lockdown that has forced much of the city's 25 million people to stay at home.

Images of workers clad in white hazmat suits sealing entrances of housing blocks and even closing off entire streets with roughly 2m-tall green fencing went viral on social media on Saturday (April 23), prompting questions and complaints from residents.

"This is so disrespectful of the rights of the people inside, using metal barriers to enclose them like domestic animals," said one user on social media platform Weibo.

One video showed residents shouting from balconies at workers trying to set up fencing before relenting and taking it away. Other videos showed people trying to pull fences down.

"Isn't this a fire hazard?" asked one user on social media platform Weibo.

Another said: "This is so disrespectful of the rights of the people inside, using metal barriers to enclose them like domestic animals."

Many of the fences were erected around compounds designated “sealed areas” - buildings where at least one person tested positive for Covid-19, meaning residents are forbidden from leaving their front doors.

It was not clear what prompted authorities to resort to fencing. A notice dated Saturday from one local authority shared online said it was imposing “hard quarantine” in some areas.

Reuters was not able to verify the authenticity of the notice or all of the images, but saw green fencing on a street in central Shanghai on Sunday.

This week, Reuters has also seen police in hazmat suits patrolling Shanghai streets, setting up road blocks and asking pedestrians to return home.

The Shanghai government did not respond to a request for comment.

Most of the barriers appeared to have been erected around compounds designated as "sealed areas", which are buildings where at least one person has tested positive for Covid-19 and whose residents are forbidden from leaving their front doors.

Reuters was not able to verify the authenticity of all the photos and videos.

Shanghai, China's largest city and most important economic hub, is battling the country's biggest-ever Covid-19 outbreak with a policy that forces all positive cases into central quarantine facilities.

The lockdown, which for many residents has lasted over three weeks, has fuelled frustration over difficulties accessing food and medical care, as well as over lost wages, family separation, conditions at quarantine centres and censorship of efforts to vent online.

It has also exacted a toll on the world's second-largest economy, with factory efforts to resume production disrupted by snarled supply chains and difficulties faced by locked-down residents returning to work.

In the past week, authorities have also transferred entire communities, including uninfected people, saying they need to disinfect their homes, according to residents and social media posts.

Many residents have turned to the Internet to vent about the lockdown and express dissent, using euphemisms and other means to battle government censors who often remove content critical of the authorities.

Videos of “Do You Hear The People Sing?”, a protest anthem from “Les Miserables”, have been widely reposted, with the title of the French musical receiving over 90 million mentions on WeChat on Saturday, the chat app’s data showed.

The city reported 39 new deaths from Covid-19 for April 23 versus 12 the previous day and by far the most during the current outbreak.

It did not report any deaths from Covid-19 during the first few weeks of its latest case surge, fuelling doubt among residents about the figures.

It has since reported 87 fatalities from Covid-19, all in the past seven days.

New case numbers ticked down slightly for Saturday, but remained in the tens of thousands.

Shanghai recorded 19,657 new local asymptomatic cases compared with 20,634 a day earlier, and 1,401 symptomatic cases, down from 2,736.

China largely succeeded in keeping Covid-19 at bay following the initial outbreak in Wuhan in late 2019, with a "dynamic zero" policy aimed at stamping out all chains of infection.

That approach has been increasingly challenged by the spread of the highly infectious but less deadly Omicron variant, which has led numerous cities to impose various levels of movement restrictions that have been a further drag on the economy.

Nationwide, China reported 20,285 new asymptomatic coronavirus cases for April 23, versus 21,423 a day earlier, with 1,580 symptomatic cases, down from 2,988.

Beijing recorded 22 new Covid-19 cases - all locally transmitted - compared with six the day before.