The protests, amid a crackdown over rising Covid cases in China, spread to eight major cities across China in a rare display of defiance that has not been seen in decades.
Most protesters complained about excessive restrictions, but some shouted slogans against Mr Xi, China's most powerful leader since at least the 1980s. In a video, a crowd in Shanghai on Saturday chanted: "Xi Jinping, step down, CCP, step down".
Police using pepper spray broke up that demonstration, but people returned to the same spot on Sunday for another protest. Reports claimed an unknown number being driven away in a police bus after being detained.
Elsewhere, videos on social media said they were filmed in Nanjing in the east, Chongqing and Chengdu in the south-west and other cities showed protesters tussling with police in white protective suits or dismantling barricades used to seal off neighbourhoods.
The Chinese government has made no comment on the protests or criticism of Mr Xi following the most widespread display of opposition to the ruling Communist Party in decades.
China's zero-Covid strategy, which aims to isolate every infected person, has helped to keep the country's case numbers lower than in the West. However, the stringent rules have led to people being confined in their homes for long periods of time – in some areas, up to four months – with some saying they do not have access to sufficient food supplies. In Beijing, residents who are allowed to leave their homes have to take a Covid test every 48 hours to be allowed to access public spaces.
Questions have also been raised over a fire in an apartment block in the city of Urumqi last week, where ten people died. Internet users have asked about whether firefighters or victims trying to escape were blocked by locked doors or other anti-virus controls. Earlier, the ruling party faced public anger over the deaths of two children whose parents said anti-virus controls hampered efforts to get emergency medical help.
Officials have eased anti-virus rules in some scattered areas, such as Urumqi and the city of Korla in Xinjiang. In Beijing, the city government announced it would no longer set up gates to block access to apartment compounds where infections are found. On Monday, the number of new daily cases rose to 40,347, including 36,525 with no symptoms.
However, the ruling party newspaper People's Daily called for its anti-virus strategy to be carried out effectively, indicating Mr Xi's government has no plans to change course.
A People's Daily commentator wrote: "Facts have fully proved that each version of the prevention and control plan has withstood the test of practice."
In some protests in Beijing, calls for Covid-related freedoms have morphed into demands for wider freedoms. “We don’t want lockdowns, we want freedom,” protesters shouted. “Freedom of the press, freedom of publishing.”
Social media users have referred to the use of the song “do you hear the people sing?” from musical Les Miserables, which was also used as a protest song during demonstrations in Hong Kong two years ago, as well as elsewhere in Asia.
Mark Clifford, president of the Committee for Freedom in Hong Kong Foundation, told The Scotsman the protests showed a “wider discontent”. There have been demonstrations outside Chinese embassies across the world in support of the demonstrators in China, as well as in Hong Kong, which is a former British colony, but was returned to Chinese rule in 1997.
Under the “one country, two systems” principle, Hong Kong citizens experienced freedoms not enjoyed by their counterparts on the Chinese mainland, until 2020, when a new national security law was introduced, sparking widespread protests there.
Mr Clifford said: “This is the first time in over 30 years that we have had this kind of protest in China and obviously it's a very different China. It's a much wealthier China, but it's also a China that's been suffering for almost three years of on-off lockdown.
"It is the marrying of this surveillance state with the pandemic restrictions and obviously, people are fed up with it. It’s also tapping into a wider discontent that goes far beyond the Covid restrictions, and it's a discontent over the increasing repression in China under Xi Jinping.
“It's really significant. And the fact that it's so widespread shows you the frustration because for every person who's out there, there are 100 or 1,000 who are not, whether they're too scared or they have other things to do.”
Students in Hong Kong have also come out in solidarity with the demonstrators in mainland China. Mr Clifford said small events had been held at the University of Hong Kong and the Hong Kong University of Science and Technology, where the police were called and, on arrival, recorded the details of two students who had been putting up posters commemorating victims of the fire in Xinjiang.
Mr Clifford added: “I was encouraged, but also surprised to see the protests in Hong Kong. And again, I think this shows the national solidarity and the fact that people are watching what's happening in other places in China and taking action into your own hands. So for Hong Kong, it seems to have been a spark that has lit discontent that simmering for many other reasons as well.”