Footage posted online shows the men on the balcony of the embassy building.
The Metropolitan Police have reportedly confirmed the incident, journalist Nahayat Tizhoosh tweeted, citing fellow journalist Laura McQuillan. The men reportedly got to the roof and police were negotiating for them to come down.
Four men have been arrested in connection with the incident, according to Iran’s Ambassador to the UK, Hamid Baeidinejad. He tweeted that more perpetrators could still be on the grounds of the embassy.
Initial reports on social media suggest the men are from a religious organization loyal to the ideas of the late Shia Muslim cleric, Grand Ayatollah Muhammad Al-Shirazi.