A man armed with a large knife who assaulted two police officers outside Buckingham Palace is being investigated by counter-terrorism officials, British police said on Saturday.
The man was stopped on Friday evening while driving in a restricted area near the palace, the London home of Queen Elizabeth, after officers spotted a blade weapon in his car.
"During the course of detaining him, two male police officers suffered minor injuries to their arm," police said. They were later discharged after treatment.
The suspect, who is in his mid-20s according to the police, was arrested on suspicion of grievous bodily harm and assault on police. He was then further arrested under Britain's Terrorism Act, the police said in another statement overnight.
Britain has been hit this year by four militant attacks in which 36 people were killed, and the country's threat level is at severe, meaning an attack is highly likely.
No members of the royal family were present in the palace at the time. The area is a magnet for tourists in Britain's capital in the peak August holiday weekend.