British police arrested a survivor of the Tiananmen Square crackdown and raided his home after he stepped out in front of Chinese President Xi Jinping's motorcade, police and campaigners said Friday.

Shao Jiang could be seen being dragged away by several police officers after he breached a security barrier and stood alone in front of the cars on Wednesday in footage aired on Channel 4 television.

London police said Jiang, a 47-year-old academic and a blogger for human rights group Amnesty International, was arrested on suspicion of "conspiracy to commit threatening behaviour".

Two Tibetan woman were also arrested with Jiang and the homes of all three were searched.

They were bailed on Thursday after being detained overnight as the investigation continues.

Xi's state visit to Britain this week has proved controversial, with campaigners accusing the British government of glossing over human rights abuses in China for the sake of investment deals.

His wife Johanna Zhang told AFP of her shock at the arrest and subsequent search of their home.

"I was really shocked. I couldn't believe that such a thing could happen in the UK," she said.

"It reminded me of the time when our home was raided by police in China before we fled, before we became political refugees. It's almost like our life in exile was turned upside down," she said.

Zhang said police had taken a computer, a laptop, a tablet and a USB key and had ordered her husband not to come within 100 metres (328 feet) of Xi.

She said he was holding up two Amnesty signs when he was arrested -- one reading "End Autocracy" and the other saying "Democracy Now".

Amnesty representative Allan Hogarth said: "This looks like a very heavy handed response to a peaceful demonstration.

"The police need to urgently explain to Shao Jiang why they entered his property and took his possessions"," he said.

London's Metropolitan Police said in a statement: "We facilitate peaceful protests... but we will also investigate possible criminality that could put the safety of London at risk."

Jiang played an "active role in the 1989 pro-democracy movement" in China, according to Amnesty's website.

He was arrested in China in 1995 and fled in 2003, initially settling in Sweden.

Hundreds -- by some estimates more than a thousand -- died after the Communist Party sent tanks in June 1989 to crush demonstrations on Tiananmen Square in Beijing, where student-led protesters had staged a peaceful sit-in to demand democratic reforms.