Hundreds gathered outside the Iranian Embassy building in west London on Saturday, resulting in two arrests, according to local news outlets and the Metropolitan Police.
Police later released a statement on X/Twitter, clarifying that one arrest was made for aggravated trespass and assault on an emergency worker, and the other was for aggravated trespass only.
One protester, according to local media, climbed onto the embassy's balcony and tore down the Iranian flag, replacing it with the pre-Islamic revolution flag and the sun flag used by Iranian opposition groups.
A short while later, the Iranian Embassy posted a picture to X, showing the current flag returned to its place on the balcony, captioned, "Iran's flag is flying high."
In response, the Islamic Republic summoned the British Ambassador to Tehran, in order to discuss the incident, Iranian state media confirmed on Sunday evening.
British Prime Minister Keir Starmer released a joint statement on Friday with the leaders of France and Germany, stating that they are "deeply concerned about reports of violence by Iranian security forces, and strongly condemn the killing of protestors."
The protests in Britain come as a response to the ongoing protests in Iran, which began on December 28 in response to soaring inflation and quickly turned political, with protesters demanding an end to clerical rule. Hundreds of protesters have reportedly been killed since late December.
The current Iranian regime has accused the US and Israel of fomenting unrest. The Iranian army said that it would “firmly safeguard national interests, strategic infrastructure, and public property." It also blamed Israel and so-called terrorist groups for the protests and vowed to “thwart the enemy’s plots.”
The country is currently experiencing a nationwide media blackout, which began on Thursday, and has prevented several international news outlets from accessing updated information about the widespread protests.
Footage seen by The Jerusalem Post and verified by BBC's Farsi channel appears to show that protesters set fire to an Islamic Republic of Iran Broadcasting (IRIB) office in Isfahan during the protests.
Israel's Foreign Ministry's Farsi social media account has sent out various messages of support to the protesters, including sharing information on the internet outages.
"Qom, Mashhad, Tehran, Dezful. All of Iran is under the feet of the people of Iran," the ministry wrote on X/Twitter.
"The Islamic Republic has cut off people's internet. Why?" the ministry accused.
Alex Winston, James Genn, and Goldie Katz contributed to this report.