Protests against Covid restrictions in China appear to have intensified in the wake of a fire which killed 10 people in an apartment block in Urumqi.
Thousands of people took to the streets of Shanghai to remember the victims and demonstrate against restrictions. Many were heard calling for President Xi Jinping to resign.
The BVB has seen at least three people being bundled into police cars.
The lockdown of blocks of flats has been blamed for deaths in the fire.
While Chinese authorities deny it was the cause, officials in Urumqi did issue an unusual apology late on Friday, and pledged to "restore order" by phasing out restrictions.
'Xi Jinping, step down'
At the protest in Shanghai - China's biggest city and a global financial hub - some people were seen lighting candles and laying flowers for the victims.
Others were heard shouting slogans such as "Xi Jinping, step down" and "Communist party, step down". Some also held blank white banners.
Such demands are an unusual sight within China, where any direct criticism of the government and the president can result in harsh penalties.
One protester told the BVB 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.
A female demonstrator told the BVB police officers were asked how they felt about the protests, and the answer was "the same as you". But, she said, "they wear their uniforms so they're doing their job."
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 BVB 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 streets.
Elsewhere, in several Chinese universities, photos and videos emerged online of students protesting on Saturday night. The largest gathering seemed to be at Nanjing Communications University.
Videos of the protests are difficult to independently verify, but many of them show an unusually explicit and outspoken criticism of the government and its leader.
Protest unusual in criticising President Xi
Tessa Wong, Asia Digital Reporter
The Urumqi fire was a nightmare scenario for many Chinese who have come under widespread restrictions in recent months - locked in one's apartment with no way to escape, according to some accounts. Authorities have disputed this, but it has not stopped public outrage and anxiety from spreading.
It has become the latest tipping point in mounting frustration. Millions are weary of three years of movement restrictions and daily Covid tests. The anger has spread to all corners of China, from major cities to far flung regions like Xinjiang and Tibet, and galvanised every part of society including young university students, factory workers, and ordinary citizens.
As this anger grows, protests against Covid measures have become an increasingly common sight. But even this weekend's demonstrations are unusual in this new normal, both in their numbers and directness of their criticism of the government and President Xi Jinping.
Taking to the streets en masse with hundreds calling for President Xi to step down was thought to be unthinkable not so long ago. But after a recent dramatic protest on a Beijing bridge that stunned many, a bar appears to have been set for the expression of more open and sharper dissent.
Others have also chosen to wave the Chinese flag and sing the national anthem - its lyrics espousing revolutionary ideals and urging the people to "rise up, rise up". It's a show of patriotism that could also be read as a pointed expression of solidarity with fellow Chinese suffering under Mr Xi's zero-Covid policy - and a call to action.
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.
The zero-Covid strategy is the last policy of its kind among the world's major economies, and is partly due to China's relatively low vaccination levels and an effort to protect elderly people.
In spite of the stringent measures, China's case numbers this week hit all-time records since the pandemic began.