British police arrested four people who had climbed on to a balcony of the Iranian Embassy in London and waved flags in an apparent protest against the government in Tehran.
London police said on March 9 that the four men, who remained in custody, were arrested on suspicion of criminal damage and being unlawfully on diplomatic premises.
The men, who did not manage to get inside the building, came down voluntarily after around three hours.
Images posted on social media showed four men in black clothing on the balcony of the embassy, waving a blue and white flag.
Iranian Foreign Ministry spokesman Bahram Ghasemi said Tehran protested to the British government over the incident, according to the IRNA state news agency.
The report said supporters of an "extreme cult" living in Britain were responsible.
Iran's Deputy Foreign Minister Abbas Araghchi protested to the British ambassador in Tehran, demanding "absolute protection of our diplomats in London and immediate dealing of the police with the attackers," IRNA reported.
Britain's Foreign Office spokesman said in a statement: "The safety and security of diplomats and diplomatic missions in the U.K. is of paramount importance to us."
In 1980, six gunmen who supported a dissident Iranian group took over the Iranian Embassy in London, taking more than two dozen hostages.
After a six-day siege, British special forces raided the building, killing five of the gunmen and arresting another. Two of the hostages also died.