Shanghai recorded 39 Covid deaths on Sunday, the most significant day toll in weeks, while China's capital Beijing warned of a "grim" situation due to soaring infection rates.

In combating a COVID-19 epidemic, Shanghai officials have installed mesh barriers outside some residential structures, igniting further public outrage over a lockdown that has forced the majority of the city's 25 million residents to stay at home.

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

The world's second-largest economy has been battling its worst Covid-19 epidemic in two years, employing a playbook of tough lockdowns and mass testing while adhering to a strict zero-Covid policy, which has taken a heavy toll on businesses and public morale.

Shanghai's trendy business district has been virtually shut down since the beginning of the month, clogging supply chains and stranding many inhabitants in their homes for even longer as the outbreak's epicenter.

China's most significant metropolis revealed its first fatalities on April 18, despite thousands of cases reported daily over the previous weeks.

It reported 39 further deaths on Sunday, raising 87, while the country recorded over 22,000 new local virus infections.

Shanghai, China's largest metropolis and commercial powerhouse, is tackling the country's largest-ever COVID-19 outbreak with an extermination strategy that entails testing, tracing, and forcing all positive patients into central quarantine facilities.

The lockdown has lasted more than three weeks for many residents and has fueled frustration over access to food and medical care, lost earnings, family separation, quarantine conditions, and suppression of internet venting.

Pang Xinghuo, a health official, said preliminary findings indicated that Covid had been "spreading invisibly" throughout the capital for a week, affecting "schools, tour groups, and many families."

"The risk of continued and hidden transmission is high, and the situation is grim," Beijing Municipal Party Committee member Tian Wei told a press conference.

"The whole city of Beijing must act immediately."