The 26-year-old attacker stopped his car near a police vehicle in a restricted area outside the world famous palace at around 8:35pm Friday (1935 GMT), according to a Metropolitan Police statement.
“Officers spotted a large knife in his vehicle and went to arrest him,” said the statement. “During the course of detaining the man, two male police officers suffered minor injuries to their arm.”
The officers required hospital treatment but have been discharged, according to police.
The man, who was initially arrested on suspicion of causing grievous bodily harm and assaulting police, was later arrested under the Terrorism Act 2000.
“Detectives from the Metropolitan Police’s Counter Terrorism Command are now investigating the incident,” police said.
The incident comes with Britain and much of Europe on high alert following a string of major attacks over the past two years — most of which have been claimed by, or blamed on, jihadists — and hours after a knife attack on soldiers in Brussels.
In Britain alone a total of 35 people have been killed in three attacks in London and Manchester since March.
Two of those involved a vehicle ploughing into pedestrians.
The other attack was a bombing in May at a pop concert by US star Ariana Grande in the Manchester which killed 22 people including children.
– ‘Brave actions of officers’ –
The assailant in Friday’s attack was arrested on suspicion of grievous bodily harm and assault, and taken to a London hospital for treatment of minor injuries.
He has now been taken to a central London police station for questioning, police said.
“The quick and brave actions of both officers meant that the suspect was detained very quickly,” said police officer Guy Collings.
“No members of the public had any interaction with this individual at the scene. It is too early in this investigation to speculate any further.”
Social media users posted videos of a fleet of police cars and ambulances outside the palace, with the surrounding roads sealed off as police searched the area.
Twitter user Amir Jan Malik wrote: “Stuck outside Buckingham palace with many armed police officers. Heavy rifles on display traffic at a halt.”
Eyewitness Kiana Williamson told the Press Association that “there was one police van and one car, there was also a civilian’s car that had veered towards the police car”.
“They were trying to get the man out of the car, shouting, more police were arriving on to the scene and the man was fighting back,” she said.
“The man had been restrained and looked almost unconscious by the side of the road.
“I didn’t see the car driving but the car had been left at the side of the road and an eye witness had said that he had driven towards the police car,” she added.
The incident occurred just two hours after a knifeman attacked two soldiers in Brussels in what authorities are treating as a terrorist attack.
The queen was at her Balmoral residence in Scotland, although the palace said it would not comment on security issues.