Videos posted on social media showed hundreds of students gathered Monday in a courtyard at Sharif University of Technology in Tehran, a wellspring of anger at the cleric-led government. The university said 13 of its students and alumni were killed when the plane was shot down. 

"They killed our elites and replaced them with clerics!" the students shouted.

There were signs that the government, forced onto the defensive, was pursuing a harsher crackdown on the demonstrations. Videos from Sunday night showed demonstrators fleeing from tear gas and in one case a woman bleeding from the leg - a wound that protesters said was caused by live ammunition. In other videos posted on social media, which could not immediately be verified, sounds of gunfire could be heard at protests in Azadi Square in the capital, as well as in the city of Shiraz. 

The fury at Iran's government marked a stunning turnaround for leaders in Tehran, after a U.S. drone strike killed Iran's Quds Force commander, Maj. Gen. Qasem Soleimani, earlier this month, prompting hundreds of thousands of Iranians to rally in a display of public mourning. 

But the pro-government sympathy has been eclipsed in recent days by unexpected and striking tableaux of popular rage and grief. Protesters have confronted heavily-armed police officers at universities and in public squares and torn down posters of Soleimani, a potent symbol for the government of its power and regional ambitions. 

Elsewhere, the government had been forced to replace Soleimani's portrait with messages mourning victims of the crash. Journalists working for state media have resigned, and one apologized on social media for misleading the public for years. 

"The regime is struggling to manage this crisis," said Nader Hashemi, the director of the Center for Middle East Studies at the University of Denver's Josef Korbel School of International Studies. "One week ago they were in control of the narrative. They were able to exploit themes of anti-imperialism and nationalism to cover up the internal crisis in Iran," he said, referring to popular anger at the country's faltering economy and government corruption. 

But everything changed after its admission of culpability for shooting down the Ukrainian airliner - the first such admission in decades, he said. "This immediately produces demands for accountability," he said. 

Soleimani's death on Jan. 3 prompted Tehran to retaliate against the United States, firing more than a dozen ballistic missiles at Iraqi military bases hosting U.S. troops.

In the hours after those attacks early Wednesday, Iran's Islamic Revolutionary Guard Corps shot down Ukraine International Airlines Flight 752 with a surface-to-air missile, a move it blamed on "human error." Listed among the dead were 82 Iranians, 57 Canadians and 11 Ukrainians, including the crew. Most, if not all, of the Canadians were reported to be of Iranian origin or dual nationals.

Iranian officials initially denied reports that the plane was brought down but later admitted that the Revolutionary Guard, which maintains military bases in the area of the crash, shot it down by mistake. The protest that began in the aftermath became the second major wave of protests to buffet the Iranian government in less than three months. 

An earlier wave, in November, brought out working-class protesters and focused on economic hardship. The demonstrations over the last three days included middle-class citizens in Iran's cities, showing a broadening of the discontent, analysts said.

"People feel like they are lied to, and there are coverups, and there is incompetence," said Hadi Ghaemi, the New York-based founder and executive director of the Campaign for Human Rights in Iran.

The government appeared to be trying to avoid the mass casualties during the November protests, when Iranian security forces killed at least 200 protesters amid unrest over cuts to fuel subsidies across the country, according to rights groups. The Trump administration has put the death toll from those demonstrations much higher, saying that some 1,500 people were killed by security forces. 

Ghaemi said that in the latest protests security forces initially tried to clear the crowds with tear gas before using rubber bullets.There were some accounts of live ammunition used at around 11 p.m. on Sunday night in Tehran, he said, adding, "They certainly took care to not commit a massacre like in November."

In a televised statement, Tehran's police chief denied that police shot at protesters and said they are under orders to show restraint.

"Police treated people who had gathered with patience and tolerance," Iranian media quoted Brig. Gen. Hossein Rahimi as saying, the Associated Press reported. "Police did not shoot in the gatherings since broad-mindedness and restraint has been agenda of the police forces of the capital." 

Residents reported a heavy security presence in central Tehran on Monday, including riot police and uniformed officers. One video showed riot police gathered near Vali-e Asr Square. 

"All of Enghelab Street until Azadi Square is full of security forces," said Sahar, 32, a resident of Tehran. Like other Iranians interviewed for this article, she declined to give her full name for fear of government reprisal. 

Ali Rabiei, a government spokesman, said Monday that Iran's military should be commended for accepting responsibility for downing the airliner and that the government would emphasize transparency in the investigation going forward. 

Official statements of regret have so far failed to assuage an angry public, including people close to the government. 

The official Islamic Republic News Agency published a searing statement from the Tehran Province Association of Journalists on Monday decrying the state of media in Iran. 

"What endangers this society right now is not only missiles or military attacks but a lack of free media," the association said. "Hiding the truth and spreading lies traumatized the public. What happened was a catastrophe for media in Iran." 

At least three anchors on Iranian state television have announced their resignations since the crisis began. The latest was Gelareh Jabbari, who posted a message on Instagram Sunday, apologizing to her audience for "Having lied to you on Iranian TV for thirteen years."

"I will never go back to TV," she added.

In a statement, students at the Amir Kabir University of Technology in Tehran, another site of recent protests, criticized the government, saying that "in the past two months, the regime's dysfunction has been proven - it's a regime that has only one answer to any problem: oppression." 

"We know that America's presence in the Middle East has caused chaos and turmoil, and we object to the presence of any invading power," the statement continued. The U.S. presence in the region "must not turn into an excuse for internal repression," it added.