Explosion near BA offices in Tehran

Embassy spokeswoman Mitra Behnam Mojtahedi said the bomb exploded on the 10th floor of a building where the airline's offices are located. She said it was not clear if the target was British Airways, as other foreign companies have offices on the same floor, such as BP, Lloyds and Mercedes Benz.

But British Airways offices were the closest to the bomb, which was placed next to the stairs' door.

Mojtahedi said the explosion broke some windows of the Sayeh Building in Vali-e-Asr Avenue, but nobody was wounded. Police are investigating, she added.

In recent weeks, the British Embassy has been the site of numerous demonstrations against Western pressure over Iran's nuclear programme. But today's explosion was the first time that a British company appears to have been targeted.

Britain, as well as France and Germany, had been negotiating with Iran in a bid to persuade it to abandon uranium enrichment. Iran refused, and the UN nuclear watchdog warned it could be referred to the Security Council.