Thousands of protesters took to the streets of Shanghai, where the BBC saw people being bundled into police cars.
Students have also demonstrated at universities in Beijing and Nanjing.
The latest unrest follows a protest in the remote north-west city of Urumqi, where lockdown rules were blamed after 10 people died in a tower block fire.
While Chinese authorities deny that Covid restrictions caused the deaths, officials in Urumqi did issue an unusual apology late on Friday, and pledged to “restore order” by phasing out restrictions.
At the protest in Shanghai – China’s biggest city and a global financial hub in the east of the country – people were heard openly shouting slogans such as “Xi Jinping, step down” and “Communist party, step down”.
Some held blank white banners, while other lit candles and laid flowers for the victims in Urumqi.
Such demands are an unusual sight within China, where any direct criticism of the government and the president can result in harsh penalties.
But analysts say the government appears to have drastically underestimated growing discontent towards the zero-Covid approach, a policy inextricably linked to Xi Jinping who recently pledged there would be no swerving from it.
One protester in Shanghai told the BBC that he felt “shocked and a bit excited” to see people out on the streets, calling it the first time he’d seen such large-scale dissent in China.
He said lockdowns made him feel “sad, angry and hopeless”, and had left him unable to see his unwell mother, who was undergoing cancer treatment.
Others gave accounts of violence, with one protester telling the Associated Press news agency one of his friends had been beaten by police at the scene, while two others had been pepper sprayed.
Though the situation in the area had calmed by Sunday morning, the BBC saw a heightened police presence in the area of the protest, with several dozen police officers, private security guards and plain-clothed police officers on
The protests are the latest in an accelerating series of demonstrations against China’s zero-Covid measures which have also become increasingly bolder in criticism of the government and President Xi.
BBC