A fan set off a firecracker similar to those used during sports matches to express his excitement at Iranian President Mahmoud Ahmadinejad's visit to the western Iranian town of Hamedan, reported the IRNA news agency. The explosion near the president's convoy had set off a flurry of media reports, including one that it was a handmade grenade.
The conservative Iranian website, khabaronline.ir, said a grenade exploded as the president's convoy headed from the airport to the venue for the speech, but did not harm him.
Eyewitnesses in Hamedan told The Associated Press by telephone that the explosion definitely came from a firecracker.
"It was a firecracker, which made a sound and produced smoke near where I was standing," Amin Mehrabi said. "Many people filmed it with their cell phone cameras."
Irans deputy police chief, Gen. Ahmad Reza Radan told the state news agency the reports about the explosion were "sheer lies" circulated by foreign media.
Ahmadinejad went on to give his speech as planned, and it was broadcast live on state television. He made no mention of the attack in his remarks, focusing instead on the country's disputed nuclear program.
He struck a hard line against Western demands that Iran halt its nuclear activities. The U.S. and its allies accuse Iran of trying to develop atomic weapons, but Tehran insists its nuclear program is for peaceful purposes.
"It will be one of your big mistakes if you think you, resorting to lies and hue and cry, are able to achieve something and we will give you any concessions," Ahmadinejad told the crowd at the Hamedan stadium.
One person was arrested in connection with the attack, the website report said, adding that Ahmadinejad's car was about 100 yards (meters) from the blast. It also said there was no information whether anyone was injured.
"The explosion caused a lot of smoke," the report said. Ahmadinejad, whose popularity at home is waning amid a faltering economy and tightened U.N. and Western sanctions over Tehran's nuclear program, regularly tours the countryside to deliver speeches to grass-roots supporters in cities and town across Iran.
A U.S.-Iran relations specialist, Jim Walsh with the MIT program on security studies, said that "Iran has a strong interest in trying to minimize this event, given the domestic problems following last year's unrest over the presidential election."
Walsh stressed that assassinations have been a staple of Iranian politics in the past and that while there have been attempts on other Iranian officials, there's been no known such attack on Ahmadinejad.
Several media outlets differed in the details about what happened.
The semiofficial Fars news agency said a handmade grenade was thrown at the path where the president and his entourage had been but only after they had left the site.
The semiofficial Mehr news agency called it a handmade percussion grenade, adding that there were several arrests.
A photo by the semiofficial ISNA news agency showed smoke dozens of yards away from the convoy, which was surrounded by people. It did not elaborate on the source of the smoke.
Hamedan, 200 miles (340 kilometers) west of Tehran, is not known as a restive area, but it is close to Kurdish area of Iran that has witnessed occasional clashes between Kurdish rebels and security forces over the past years.
Ahmadinejad also said Monday during a speech that Israel had sent agents to assassinate him, but he gave no details.
The accusation came a day after another conservative Iranian website, Mashreghnews.ir, reported that security forces had detained a terrorist group in Tehran that planned to assassinate officials. It linked the group to Kurdish separatists.
In May, Ahmadinejad was jeered by a crowd demanding jobs when he was speaking during a similar visit to the southern Iranian town of Khorramshahr.
In 2005, bandits reportedly killed a bodyguard of Ahmadinejad during his visit to restive Sistan-Baluchistan province in southeastern Iran. However, the president had left the province before the attack occurred.
Associated Press Writer Katarina Kratovac contributed to this report from Cairo.