Video from the scene in Shanghai showed police seizing and then carrying away one protester.
The wave of civil disobedience is unprecedented in mainland China, where room for dissent has been all but eliminated under President Xi Jinping, as frustration mounts over his signature zero-COVID policy.
Protesters also took to the streets in the cities of Wuhan and Chengdu on Sunday.
In Beijing, small gatherings held peaceful vigils, while students on numerous university campuses around China gathered to demonstrate over the weekend.
The protests come after a deadly apartment fire on Thursday in the country's far west, where millions of residents have been under some of the country's longest lockdowns, barred from leaving their homes for as long as 100 days.
Video obtained by Reuters showed residents chanting "lift the COVID lockdown" and arguing with guards in hazmat suits after the fire led to accusations that lockdowns were a factor in the blaze that killed 10 people.
Officials have denied that COVID measures hampered escape and rescue efforts.
China has stuck with Xi's zero-COVID policy even as much of the world has lifted most restrictions. While low by global standards, China's case numbers have hit record highs for days, with nearly 40,000 new infections on Saturday, prompting yet more lockdowns in cities across the country.
