Counter-terror police are investigating an incident where a car crashed into the barriers outside the House of Lords, injuring pedestrians.
The crash happened at around 7.30am, and a man in his 20s was arrested at the scene on suspicion of terror offences.
The driver of the vehicle is in custody in a police station in South London, and police said nobody else was in the vehicle.
The car is still at the scene being searched, and no weapons have been found.
The injured pedestrians were taken to hospital, and injuries are not thought to ve life-threatening.
Eyewitnesses said a man was removed from the car and led away in handcuffs.
Transport for London tweeted that surrounding roads were closed.
Eyewitness videos and photos showed police on the road and sirens could be heard.
The Metropolitan Police said a man had been detained at the scene, and a number of pedestrians had been injured.
Anyone with information is urged to call 0800 789 321.