A 'knifeman' has been arrested after two police officers were injured in an attack outside Buckingham Palace in front of terrified tourists.

Witnesses reported seeing police armed with guns swarming the scene after a man was spotted with a knife on the Mall at about 8.35pm on Friday.

The man, believed to be aged in his early 20s, was stopped when officers spotted a large knife while he was in his car, Scotland Yard said.

They were attacked as they tried to make an arrest, suffering minor injuries to their arms. Both were treated at the scene.

No other people were injured in the attack.

Bystanders originally reported on social media that the attacker was armed with the sword, but the Met later described it as a "large knife"

Witnesses took to social media, describing Buckingham Palace as "on lockdown" as police officers put a large cordon in place.

The man was arrested on suspicion of grievous bodily harm and assault on police.

Witness Nicole Kyle was walking home when she saw armed police swoop on the scene.

The 25-year-old consultant said: "I was walking toward The Mall and St James's Park when I saw police rush down toward the palace in great numbers.

"As we got further down The Mall we saw armed police outside a police van, at which point we were able to walk closer to the palace still, where we were eventually stopped by a cordon. All we were told was that there's been an incident.

"A few minutes later police came by to have us clear the area and move further away from the palace.

"We then saw that police had expanded the cordon. It looks like the cordon is continuing to expand."

Detective Superintendent Guy Collings said: “A man in his mid-twenties has been arrested by police after they spotted a weapon inside his car.

"The quick and brave actions of both officers meant that the suspect was detained very quickly.

"No members of the public had any interaction with this individual at the scene. He will now be questioned by detectives in police custody. It is too early in this investigation to speculate any further.”

The Queen was not in residence when the attack happened.