Police have been accused of manhandling a Tiananmen Square survivor away from a human rights protest before raiding his home.
Shao Jiang, 47, was seized outside Mansion House in central London shortly before Chinese president Xi Jinping arrived at the venue.
Footage shows Mr Jiang standing in the road waving banners before a group of officers dash over and drag him away.
Two other women, Sonam Choden, 30, and Jamphel Lhamo, 33, were also arrested at the scene.
Campaigners have accused the Met Police of deliberately targeting Tibetan demonstrators to try to please China.
Tsering Passang, of the Tibetan Community in Britain group, said: "The police were extremely over-handed and it shouldn't have been done that way.
"I was totally shocked at what happened, it was so unnecessary.
"This is Britain and it shouldn't be like that.
"They were campaigning for human rights and freedom in Tibet and China.
"These people were treated as if they were terrorist activities or something, it's too much."
All three campaigners allegedly had their houses raided by police, who seized computers and phones.
Allan Hogarth, Amnesty International, said: "The video that has emerged looks like a very heavy handed response to a peaceful demonstration."
He added: "Shao Jiang has witnessed a lot in his life. All he wants is to highlight the human rights abuses that are being committed in China.
"It is deeply worrying that the UK Government appears keen to push human rights to one side in pursuit of trade.
"The UK must ensure human rights are a priority and they must not shirk from raising human rights with those it does business with."
The Met Police confirmed a man and two women were arrested at around 4.30pm on Wednesday.
"Officers on the security operation for the visiting Chinese president arrested a man in the Bank area to prevent a breach of the peace," a spokesman said.
"Two women were arrested nearby shortly after, also to prevent a breach of the peace.
"All three were further arrested on suspicion of conspiracy to commit threatening behaviour."
All three have been released on police bail.