A few hours after the incident, Metropolitan Police announced that detectives from its Counter Terrorism Command are investigating.
At approximately 8:35 p.m., "a man stopped his car in a restricted area near a police vehicle on the Mall roundabout near Spur Road," Metropolitan Police said in statement. "Officers at the Mall spotted a large bladed weapon in his vehicle and went to arrest him."
A 26-year-old man was arrested at the scene on suspicion of grievous bodily harm and assault on police. He was further arrested under the Terrorism Act 2000.
The suspect was taken to a London hospital for treatment of minor injuries. He was then taken to a police station for questioning.
During the course of detaining the man, two male police officers suffered minor injuries to their arm. Both injured officers were taken to hospital for treatment and have since been discharged.
There were no other reported injuries.
The Queen was not at Buckingham Palace at the time of the incident.