A man has been arrested on suspicion of criminal damage and dangerous driving after a vehicle was driven into the gates of Downing Street in London.
The silver Kia car crashed into the gates at around 4.20pm today, the Metropolitan Police said in a statement.
Images on social media showed the car surrounded by emergency vehicles.
The man was arrested by armed officers, the force said, and nobody was injured.
It is understood that counter-terrorism police are not involved in the investigation at this stage.
It is understood that British Prime Minister Rishi Sunak was in 10 Downing Street at the time.
He had been due to leave the building and departed after the crash.
Witness Simon Parry, 44, said he heard a "bang" and saw police pointing Taser guns at a man.
"I heard a bang and looked up and saw loads of police with Taser guns shouting at the man.
"A lot of police vehicles came very quickly and were very quick to evacuate the area."
Mr Parry said the driver had his "face to the floor" as he was being arrested.
He said the man appeared to slow down before he reached the gates of Downing Street, having driven out from the other side of the road.
"There were sniffer dogs and a bomb squad," he added.
Asked to describe the mood in the immediate aftermath, Mr Parry said: "We saw people that were in a panic running away and we saw people who were excited."
Footage of the incident broadcast by the BBC appears to show the car slowing down before it hits the gate.
The incident came as many civil servants were leaving work.
A police cordon was initially put in place in the Whitehall area outside Downing Street, but was later removed.
A tow truck then transported the vehicle from the area.