British police jostled with demonstrators as they blocked the road to the embassy, which appeared to earlier have had red paint thrown at it.
Officers detained at least one protester here.
Several attendees waved the national flag of Iran that was used prior to the 1979 Islamic revolution.
And clashes also broke out in northwest London during protests connected to the death of a woman in Iran.
British riot police were deployed to the scene of the clashes, which occurred near Marble Arch in central London and near the Islamic Centre of England, 3 kilometres to the northwest.
Demonstrations erupted across Iran more than a week ago at the funeral of a 22-year-old Kurdish woman named Mahsa Amini, who died in detention after being arrested by police enforcing the Islamic Republic's strict restrictions on women's dress.
They have turned into the biggest Iranian protests in years and countries around the world have seen protests of solidarity in recent days.
Iran summoned the British and Norwegian ambassadors over what it called interference and hostile media coverage of the nationwide unrest.
Reuters