A man sparked a major security alert Thursday after a car crashed into the gates of the UK prime minister's Downing Street complex in London, but police said they were not currently treating it as "terror-related".

Armed officers arrested the man at the scene on suspicion of criminal damage and dangerous driving, shortly after the vehicle "collided with the gates of Downing Street" at around 16:20 pm (1520 GMT), London police said.

No injuries were reported. Prime Minister Rishi Sunak was reported by British media to have been in the building -- which hosts both his office and residence -- when the incident occurred and left soon after.

Video footage showed a silver car driving at low speed across Whitehall, where many government ministries are located, having emerged from a gated area next to the Ministry of Defence, opposite Downing Street.

It appeared to then mount the footpath and came to a halt after hitting the large metal gates that guard the entrance to Downing Street.

Other footage showed a police cordon surrounding the car, which appeared to be a Kia, with its boot open.

Around two hours after the incident, London's Metropolitan police said in an update that a small cordon remained in place outside Downing Street, with the car still within it.

"The incident is being dealt with by local officers in Westminster and isn't currently being treated as terror-related," the force added