Yu Wensheng was seized Friday by roughly a dozen police, including a SWAT team, as he left his Beijing apartment to walk his child to school, sources said.
Yu, best known for suing the Beijing government over the city's once chronic pollution, has been a persistent voice for reform despite an increasingly severe crackdown on activism under President Xi Jinping.
The video, taken by a police body cam and published Tuesday by state media outlet The Paper, showed police surrounding the 50-year-old on a street before dawn and telling him he was to be detained for "provoking trouble".
Yu's 13-year-old son -- who had run back home to tell his mother what happened, according to defence lawyer Huang Hanzhong -- did not appear in the video.
In the footage Yu repeatedly tells officers "I will not obey," then throws a right hook at an officer before being subdued, though it is unclear if he landed the punch.
The video appears to be edited: time stamps jump back and forth at several points.
"An unedited video is not available so it's hard to say what happened, but it looked like it was taken during Yu's arrest," Huang told AFP.
The video appears to show that police did not present Yu with a written summons notice, Huang said, a possible violation of Chinese law.
Police appeared to be trying to provoke him by deploying three cars and a dozen officers, he said.
They have not allowed Yu to meet his lawyer or family since his arrest.
He was charged with disrupting a public service, according to a detention order seen by AFP.
Huang said the charge referred to Yu's altercation with the police, a crime that carries a maximum three-year jail sentence.
It does not explain why the police were at Yu's apartment in the first place, however.
The video was "obviously heavily edited" to suggest Yu had spontaneously engaged in unprovoked violence towards police, according to William Nee, China researcher at Amnesty International.
"It is consistent with the government's attempt to smear the image of human rights defenders more broadly," he said.
State media often shows televised "confessions" from suspects in detention or on bail, a tactic that lawyers say violates their right to a fair trial.
"I've not seen (another) video of a human rights lawyer or any human rights activist getting arrested. I think the authorities are smearing him," said Human Rights Watch China researcher Maya Wang.
(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)
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