A conservative Iranian website had said an explosive device was thrown at his convoy in the western city of Hamedan, where he was to deliver a speech, but later removed the report from its site.

State-run Press TV said “no such attack had happened”, and officials said the blast was caused by a firework.

Security is actually not that tight around President Ahmadinejad when he is out on tour.

Presidential tours are announced in advance, and he is swamped by crowds even though there are security guards around him.

If confirmed as an assassination attempt, it would be the first one I have heard of during his presidency, although the president claimed the Americans had a plot to kidnap him when he travelled to Iraq a couple of years ago.

Mr Ahmadinejad went ahead with his speech at a football stadium.

“It was a firecracker, and a statement will be released soon,” an official in the president’s media office told the Agence France-Presse news agency.