The British embassy in Tehran was hit by a firebomb on Friday, with the broad daylight attack causing some fire damage to the mission's gate but no casualties, a British diplomat said.

"At around 3:30 this afternoon (1200 GMT), somebody drove by and threw a small firebomb at the Churchill Gate. There was fire damage on both sides of the gate but nobody was injured," the diplomat said.

"We are in contact with the Iranian authorities over this incident."

The diplomat said the firebomb appeared to have been lobbed from a passing car.

The embassy was the target of a spate of drive-by shootings in September, and Iran claims to have detained suspects in connection with the earlier attacks.

NGO hit in Iraq

Meanwhile, another explosion occurred outside the office of a British-based mine clearance agency in neighbouring Iraq, in the northern city of Arbil on Friday, but there were no immediate reports of casualties, security officers at the scene said.

A small petrol tanker was destroyed in the blast, which smashed windows in the Mine Action Group's two storey office building. No structural damage was visible. There were conflicting reports as to what had caused the explosion.

Emergency vehicles raced to the scene and security forces sealed off surrounding streets after the blast.

Arbil's governor Akram Moutak and Karim Sinjari, the interior minister of the Kurdish regional government, inspected the scene of the explosion but declined to speak to reporters.

Week of violence

Bomb attacks on the British consulate and HSBC bank in Istanbul killed at least 27 people on Thursday. Five days earlier, car bomb attacks on two synagogues in the city had killed 25.

Both Istanbul attacks have been claimed by al-Qaida and a local Islamist group Islamic Front of Raiders of the Great Orient.