State television has repeatedly shown images, ostensibly taken during, of unidentified hands burning and tearing up pictures of Ayatollah Ruhollah Khomeini. It was a grave and illegal insult against the former leader still widely respected in the country, and the elite Revolutionary Guard, the country's most powerful military force, called for the trial and punishment of those responsible.
Video circulated widely on the Internet on the day of last week's protests also showed photos of Supreme Leader Ayatollah Ali Khamenei and President Mahmoud Ahmadinejad being burned, as well as one photo of Khamenei and Khomeini side by side going up in flames. The faces of those burning the pictures could not be seen and loud chants against the government were heard in the background.
Khamenei, who has the final say on all state matters, appealed for calm but suggested the opposition was creating a hostile environment.
"Some have converted the election campaign into a campaign against the entire system," he said without naming any opposition leaders. "We call on those who are angry to remain calm."
Students, who led Sunday's protests, contended the images of burning photos were fabricated by government agents as a pretext for further crackdowns on the opposition.
Tens of thousands of students protested last Tuesday on campuses in the capital Tehran and other parts of the country, the largest anti-government rallies in months. There were also a number of demonstrations outside of campuses.
Many protesters shouted slogans against Khamenei and Ahmadinejad and chanted "Death to the Dictator."
Tens of thousands of hard-line clerics rallied in cities across the country on Saturday to denounce those who burned photos of Khamenei, the second straight day of protests by angry government supporters.
Khomeini, who led the 1979 Islamic Revolution, is revered by both the opposition and the ruling system. But Khamenei is a much more divisive figure, seen by the opposition as a dictator who rules with an iron fist.
During last week's rallies, protesters shouted "Death to the oppressor, whether it's the shah or the leader!" - making a daring comparison between Khamenei and the pro-U.S. shah, despised in Iran since his overthrow.
Opposition leader Mir Hossein Mousavi, Iran's powerful prime minister in the '80s, was strongly supported by Khomeini against Khamenei, Iran's then-president. When massive street demonstrations erupted over June's disputed presidential election, the opposition led by Mousavi borrowed tactics from Khomenei's Islamic Revolution, such as shouting "Allahu Akbar" from the rooftops of Tehran in a nightly protest.
Mousavi has said his supporters love Khomeini and would not take actions that insulted him. The opposition contends the fabricated images are being used by the regime to discredit the pro-reform movement.
Khamenei warned opposition leaders to stay away from protesters.
"Why don't they learn when leaders of oppression and arrogance, the U.S., France and Britain, support them," state TV quoted Khamenei as saying. "Open your eyes and stay away," he said.
Hundreds of pro-reform students protested against the government on the campus of Tehran University Sunday, denying the accusations they had any connection with the images. Dozens of police surrounded the campus.
The Revolutionary Guard called for the legal action against those who burned the photos of Khomenei.
"The Revolutionary Guard ... won't tolerate any silence or hesitation in the immediate identification, trial and punishment of those carrying out this ugly insult and the agents behind them," it said in a statement posted on its Web site.
Under the law, insults to the late or current supreme leader can lead to two years of prison.
The Guard, which is tasked with defending the clerical regime that came to power in Iran in 1979 under Khomeini's leadership after the pro-U.S. shah was overthrown, was at the forefront of crushing the post-election unrest.
Reformists contend that Ahmadinejad was re-elected in June by massive vote fraud that set off huge street protests. The protests evolved into a broader confrontation against the country's ruling theocracy, but eventually died down when a harsh crackdown by security forces stifled the street demonstrations.