A man has been arrested outside Buckingham Palace on suspicion of grievous bodily harm and assault after two officers were injured, Scotland Yard said.
Scotland Yard said the officers suffered minor injuries in the course of arresting the man tonight.
No other people were injured, the force wrote on Twitter.
Police said the man was stopped outside the royal grounds in possession of a knife at around 8.35pm.
The London Ambulance Service attended to treat the injured men but they were not taken to hospital.
Images posted online showed a heavy police presence outside the palace, with emergency vehicles packing out the road. Armed police were reported to be on the scene.
Twitter user Amir Jan Malik wrote: “Stuck outside Buckingham palace with many armed police officers. Heavy rifles on display traffic at a halt.”