Conservative website khabaronline.ir said a blast took place in Hamedan as Ahmadinejad was on his way to address a crowd. The president was unharmed, according to the site, and gave his speech as planned, which was broadcast live on state TV.
Not long after reports of an apparent assassination attempt swept across the world's media, an official Iranian TV channel said Iran's government "vehemently denies" that the president's convoy came under attack, blaming the explosion on a firework set off in celebration of his arrival.
Khabaronline.ir reported that one person was arrested in connection with the supposed attack, adding that the president's car was about 100 yards away from the site of the blast.
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 concession," Ahmadinejad told the crowd at the Hamedan stadium.
Khabaronline.ir's report on the apparent assassination attempt was removed from the site not long after state-run Press TV ran the government's official denial.
Adding to the confusion over the incident, the Reuters news agency said an official from Ahmadinejad's office had confirmed that the convoy came under attack and that there were injuries, though the president was not among those hurt. The official spoke to Reuters on the condition of anonymity.
CBS News security analyst Juan Zarate says, despite the Iranian regime's line on the incident, it was likely an attack on the controversial president.
Zarate says there has been simmering discontent among some members of the ruling elite in Iran over Ahmadinejad's leadership -- from both the conservative and liberal side of the domestic political spectrum.
"I think what we're going to see is that some of that is coming to the fore with this attack," Zarate told CBS' "Early Show" co-anchor Harry Smith.
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. Fars said the explosion disturbed people at the site.
The government-owned Borna news agency said somebody threw a firecracker after the convoy had passed, while the semiofficial Mehr news agency called it a handmade percussion grenade.
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.
The report from IRNA quoted an official in the governor's office saying the "firecracker did not hurt anyone and did no damage."
Hamedan, 200 miles 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.
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