A small bomb has exploded outside the offices of two British companies in the Iranian capital Tehran.
The blast happened in an office block where British Airways and oil company British Petroleum had premises. No one was injured.
Iranian police originally thought there were two bombs, but closer inspection revealed there was only one blast on the 10th floor of the block.
"One hand-made bomb exploded, it only shattered a few window panes," said police spokesman Mehdi Ahmadi.
A spokesman for British Airways said they were waiting for the latest information from the Iraninan authorities before commenting on the blast.
Another small bomb exploded outside the same offices in August.
Diplomatic relations between Britain and Tehran are strained at the moment.
Iran has recently re-started its nuclear programme, prompting fears in the West that it may be creating nuclear weapons, Sky News reports.