Shots have been fired opposite the main gate of the residential compound of the British embassy in the Iranian capital of Tehran.
The shooting took place yesterday; there were no reports of injuries.
Britain protested "strongly" to Iran last week after the second of two drive-by shootings around the British embassy in under a week.
Tensions have been rising between Tehran and London over Britain's arrest at Argentina's request of a former Iranian diplomat over the 1994 bombing of a Jewish centre in Buenos Aires that killed 85 people.
Iran has said the case is politically motivated and called for the swift release of Mr Hadi Soleimanpour, who was Iran's ambassador to Argentina at the time of the bombing. He was studying in Britain when arrested last month.