Media playback is unsupported on your device Media caption The BBC's Laura Kuenssberg witnessed the man being pinned to the ground by police

A 29-year-old man who was arrested by armed officers near an entrance to Parliament has been detained under the Mental Health Act, police have said.

The suspect was Tasered after he ran towards police on Tuesday, the Met said.

Around a dozen officers surrounded the man, who was held against a fence within the parliamentary courtyard.

He was taken to a police station for questioning and a mental health assessment before being detained.

Police originally arrested him on suspicion of trespassing at a protected site.

An eyewitness told the BBC the man had jumped over railings into the grounds of Parliament.

Image copyright EPA Image caption The suspect was tasered by police

Christopher Hope, a reporter for the Daily Telegraph, told BBC News: "I heard a scream and then looked out the window, and then about half a dozen police officers who appeared not to be armed were running towards a man.

"And then it appears the man was Tasered."

BBC political editor Laura Kuenssberg, who also witnessed the disturbance, says she saw the man on the ground, arguing and shouting at police.

Police gathered up his belongings, including what looked like a passport, before bundling him into the back of a police van, she added.

The incident happened in the same area inside Parliament's grounds as last year's terror attack.

PC Keith Palmer, who was guarding the gates, was stabbed and killed by Khalid Masood, moments after he had knocked down pedestrians indiscriminately on Westminster Bridge, killing four people. Masood was shot dead by armed officers.