(CNN) -- The Iranian president on Tuesday likened the anti-government protests during Sunday's observances of Ashura to "a theater play by the Zionists and the Americans," the state-run Islamic Republic News Agency said.
"The Iranian nation has witnessed many plays of this kind: a play ordered by the Zionists and the Americans, who had purchased the tickets to this play and were the only audience of this play," IRNA quoted President Mahmoud Ahmadinejad as saying.
Ashura is the major Shiite Muslim holy day. It marks the death of Imam Hussein, grandson of the Prophet Mohammed, as a martyr. Shiites commemorate the death of Hussein each year, climaxing on Ashura -- the 10th day of the month of Muharram -- after a 40-day mourning period.
Read more about the protests in Iran
Ahmadinejad strongly criticized the positions taken by U.S. President Obama and the British government, IRNA said. The news agency quoted the president as saying he had "advised" the two countries several times, but "they insist on experiencing humiliation."
The British ambassador to Iran, Simon Gass, was summoned to the Iranian Foreign Ministry on Tuesday "to receive Iran's complaint regarding that country's interference in Iran's internal affairs," the semi-official news agency Fars reported.
Ari Larijani, the speaker of Iran's parliament, also slammed Britain and the United States on Tuesday for condemning the government crackdown Sunday on the protesters.
Timeline: Turmoil in Iran
Video: Perspective on Iran
Video: Your questions on Iran
Video: Iran: Blood in the streets
Mir Hossein Moussavi
Protests and Demonstrations
Larijani said authorities should mete out "the harshest punishment" to protesters who disrupted Ashura observances. Addressing lawmakers, Larijani said the protesters had insulted Imam Hussein.
He urged officials to "arrest offenders of the religion and mete out harshest punishments to such anti-revolutionary figures with no mercy."
An Iranian media blackout had made it difficult to verify accounts of the weekend's violence, but videos that found their way west depicted bloodied and, in some cases, apparently dead protesters.
Are you there? Share your stories, photos and videos
In one video, posted on the Web site YouTube on Tuesday, green and white police trucks rush into crowds of protesters in Tehran. The demonstrators scatter in all directions, but one truck drives into a crowd trapped in a narrow street with a wall on one side and parked cars on the other.
The camera follows the 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 police truck drives over the person. Other protesters rush to the downed person's aid, but it was not clear whether that person was killed.
CNN cannot confirm the authenticity of the video, or another one obtained by CNN that shows a woman who was reportedly killed when hit by a car driven by members of the Basij, the Iranian paramilitary group. The video shows protesters transfering her body from a clinic near where she was killed to another hospital to keep her remains out of reach of security forces.
Abbas Jafari Dolatabadi, Tehran's chief prosecutor, said Tuesday that seven people were killed in the Ashura riots Sunday. The toll makes them the bloodiest since June, when protests over the disputed presidential election that gave Ahmadinejad a second term left at least eight dead.
The Iranian government has denied that its security forces killed anyone.
One of those reported killed was Saeed Ali Moussavi, the nephew of Iranian opposition leader Mir Hossein Moussavi. Moussavi's movement says the nephew was shot to death.
Dolatabadi said that one of those killed was fatally shot and that the case is under investigation, but he did not identify the victim. He said most of the seven deaths occurred after the people were struck with "hard objects or due to similar causes."
Mir Hossein Moussavi's Web site said the nephew was killed in the demonstrations by a shot to the heart. But IRNA said that the bullet came from a "terror team" and that other such teams were operating in Tehran. It did not offer further details.
The Mehr semi-official news agency quoted security forces Tuesday as explaining that the nephew was standing on a street at midday Sunday when he was "assassinated by firearm by the occupants of a passing vehicle, and died because of the delay in taking him to the hospital.
"He died of severe bleeding on the way to the hospital. Efforts to identify the culprit or culprits continue."
IRNA disputed an account on the reformist Web site Parlemannews, which said the nephew's body had disappeared.
It said the government is holding the body and four others for autopsies. The delay meant the dead could not be buried within 24 hours, as Islamic custom dictates.
Iran Deputy Police Chief Ahmad Reza Radan and Tehran Police Chief Azizollah Rajabzadeh denied that their forces had killed anyone. In fact, they told the semi-official Islamic Students News Agency, their forces fired no weapons and weren't even carrying firearms.
In many cases, opposition media reported, government security forces prevented observances of Ashura.
Police arrested hundreds of people, including prominent figures. Nobel Laureate Shirin Ebadi said Monday that Iranian intelligence officials had detained her sister, dentistry professor Nushin Ebadi.
IRNA, Fars and other state news agencies said there would be a pro-government march on Wednesday afternoon.