Protestors clashed with police outside the Iranian embassy, leaving a number of officers injured and five arrested for offences including violent disorder.
Online footage showed a line of officers pushing back men armed with long rods.
Hundreds of people were seen in the crowds, many waving Iranian flags, outside the building in Princes Gate, south west London.
It comes after more than a week of anti-government demonstrations following the death of Mahsa Amini in police custody, who had been detained for allegedly breaking headscarf rules.
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A spokesman for the Metropolitan Police said: "During the afternoon of Sunday, 25 September a large number of protesters gathered at the location, with a substantial group intent on causing disorder.
"Further police resources were brought in to support those on the ground after protesters attempted to breach police lines and had thrown missiles at officers.
"Five arrests have been made for offences including violent disorder.
"We are aware of a number of police officers who received injuries while dealing with the disorder; none of those are thought to be seriously hurt.
"A significant policing presence will remain in and around the area to monitor the situation."