A car carrying Boris Johnson was involved in a crash as it avoided protesters while leaving the Palace of Westminster.
A demonstrator, who had been protesting about Turkish action against Kurdish rebels, ran into the road outside the gates to Parliament in front of the convoy.
This forced the lead vehicles in the convoy - a police motorbike and the Prime Minister's Jaguar - to stop, with a support vehicle running into the back of the luxury saloon carrying the Prime Minister.
The vehicles drove off shortly afterwards in the direction of Downing Street, with a large dent visible on the rear of the Jaguar.
Downing Street said there were no reports of anyone being injured in the incident.
The protester was detained by police and taken into the Palace of Westminster by officers.
Video showed the car being hit by a Range Rover travelling behind.
A Number 10 spokesman confirmed the car was Mr Johnson's, adding: "I think the video speaks for itself as to what happened.
"No reports of anybody being injured."
The spokesman said Mr Johnson was travelling in the car at the time.
