Two British police officers have suffered minor injuries as they arrested a man carrying a knife outside Buckingham Palace.
The man was arrested on suspicion of grievous bodily harm and assault on police near to Queen Elizabeth's London residence.
The officers did not need to be treated at hospital after the attack on Friday night (local time).
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Footage on Sky News showed emergency vehicles lining the street outside the palace.
A Metropolitan Police spokeswoman said she was unable to comment at this stage on the motivation for the incident.
A Reuters witness near the scene said police had cordoned off a wide area around the palace for security.
"The man was stopped this evening, Friday 25 August ... by officers at the Mall outside Buckingham Palace in possession of knife," the police said in a statement.
"During the course of detaining him, two male police officers suffered minor injuries to their arm."