BBC:-A man was brought down with a Taser outside the Palace of Westminster after he reached for a knife when approached by officers, Scotland Yard has said.
A bearded man, wearing black trousers and a grey sweatshirt, was seen being held against the fence with his arms behind his back by a police officer.
Scotland Yard said the man was arrested on suspicion of possessing a knife.
He was held just yards from where PC Keith Palmer was stabbed to death by terrorist Khalid Masood in March.
Joe Murphy, London Evening Standard political editor, tweeted: “There were shouts of ‘knife, knife, knife’ and man was brought down with a Taser.”
BBC deputy political editor John Pienaar said the latest incident ended very swiftly with the man being taken away in a police van.
While the gates are closed, the road and pavement opposite remained open and the incident had no affect on traffic in Parliament Square, he said.