TEHRAN, Iran (CNN) -- Iranian security forces blamed a privately owned vehicle Thursday for allegedly running into protesters during Sunday's opposition protests on a Shiite Muslim holy day, according to a news agency.
"There were no deaths resulting from a car accident in the Vali-e Asr area. We referred to the fact in our previous statement that a privately owned Patrol vehicle hit a number of rioters on Azadi [Freedom] Street between Roudaki and Khosh Streets," said the semi-official Iranian Labour News Agency, referring to a model of car made by Nissan.
"The vehicle was traced by the security forces and the case is being investigated," ILNA said.
At least seven people were killed Sunday -- the Shiite Muslim holy day Ashura -- as anti-government protests turned violent. The Iranian government denies that any of the deaths were caused by official security forces, but the clashes -- depicted in sometimes grainy and shaky amateur videos -- show a number of protesters with serious and possibly fatal injuries, including some with apparent gunshot wounds.
In one video -- shot Sunday, according to the posting on the Web site YouTube -- green-and-white police trucks rush into crowds of demonstrators in Tehran. The protesters scatter in all directions, but one truck drives into a group trapped in a narrow street with a wall on one side and parked cars on the other.
The camera follows the truck, which appears to be a police truck, as it backs away, but a person briefly can be seen crumpled in the street where the truck had been. When the camera returns to the spot, another truck drives over the person. Other protesters rush to the downed person's aid. It is not clear whether the person was killed.
CNN cannot confirm the authenticity of the video, or another one obtained by CNN that shows a woman who was said to have been killed when hit by a car driven by members of the Basij, the Iranian paramilitary group.
ILNA said it released the statement Thursday from security forces "owing to the fact that a film has been shown by foreign and anti-revolution [news] networks regarding a vehicle similar to those used by Security Forces being involved in hitting a man at the Vali-e Asr Square."
"Since the film may be a fake, which is the way foreign and anti-revolution media work, the case is being investigated."
Iran's chief prosecutor, Abbas Jafari Dolatabadi, told reporters this week that seven people where killed in Sunday's clashes on the holiday of Ashura. Most died after being struck with "hard objects or due to similar causes," Dolatabadi said.
Opposition leader Mir Hossein Moussavi's nephew, Seyyed Ali Moussavi, died from a gunshot wound on Sunday. The elder Moussavi's Web site said he was killed during the demonstrations, but state-run news agencies said that Moussavi's death was not connected to the Ashura protests but "had been planned in suspicious circumstances."
Sunday's clashes were the worst since opposition protesters took to the streets for days following the disputed June 12 presidential election. At least eight people were killed during those protests.
Ashura commemorates the martyrdom of Imam Hussein, the grandson of the Prophet Mohammed, who was killed in battle in Karbala in 680 A.D.
CNN's Shirzad Bozorgmehr contributed to this report.