Seven men have been arrested on suspicion of grievous bodily harm after two people were assaulted outside the Iranian embassy.
The Met Police have said they believe the altercation happened between protesters supporting and opposing the Iranian monarchy, and there were no links to Israel.
Officers had responded to reports of an altercation in Princes Gate in Knightsbridge, west London, shortly after 09:50 BST on Friday, a force spokesperson said.
Two men were treated for injuries at the scene by the London Ambulance Service (LAS) before one was taken to a major trauma centre and the other to hospital.
Conditions have been put in place to prevent serious disorder, stopping protesters from gathering in the area until 13:00 BST on Sunday.
