Police officers in Iran opened fire into crowds of protesters on Sunday, killing at least 10 people, witnesses and opposition Web sites said, in a day of chaotic street battles that threatened to deepen the country’s civil unrest.
The protests, during the holiday commemorating the death of Imam Hussein, Shiite Islam’s holiest martyr, were the bloodiest and among the largest since the uprisings that followed the disputed presidential election last June, witnesses said. Hundreds of people were reported wounded in cities across the country, and the Tehran police said they had made 300 arrests.
News agencies, citing an opposition Web site, said that Ibrahim Yazdi, a former foreign minister and pro-democracy leader, and Emad Baghi, a prominent human rights activist, were arrested early Monday. Mr. Yazdi was an adviser to the late Ayatollah Ruhollah Khomeini, who led the Iranian revolution in 1979.
Mehdi Karroubi, an opposition leader who was among the losing candidates in the June election, was quoted Monday as saying on a Web site that the government’s actions in suppressing the protests on Sunday were even more brutal than the regime that was overthrown in the revolution, news agencies reported.
One of the dead on Sunday was Ali Moussavi, a 43-year-old nephew of the opposition leader Mir Hussein Moussavi.
The decision by the authorities to use deadly force on the Ashura holiday infuriated many Iranians, and some said the violence appeared to galvanize more traditional religious people who have not been part of the protests so far. Historically, Iranian rulers have honored Ashura’s prohibition of violence, even during wartime.
In Tehran, thick crowds marched down a central avenue in midmorning, defying official warnings of a harsh crackdown on protests as they chanted “death to Khamenei,” referring to Iran’s supreme leader, Ayatollah Ali Khamenei, who has expressed growing intolerance for political dissent in the country.
They refused to retreat even as the police fired tear gas, charged them with batons and fired warning shots. The police then opened fire directly into the crowd, opposition Web sites said, citing witnesses. At least five people were killed in Tehran, four in the northwestern city of Tabriz, and one in Shiraz in the south, the Web sites reported. Photographs of several victims were circulated widely.
Unlike the other protesters reported killed on Sunday, Ali Moussavi appears to have been assassinated in a political gesture aimed at his uncle, according to Mohsen Makhmalbaf, an opposition figure based in Paris with close ties to the Moussavi family.
Mr. Moussavi was first run over by a sport utility vehicle outside his home, Mr. Makhmalbaf wrote on his Web site. Five men then emerged from the car, and one of them shot Mr. Moussavi. Government officials took the body late Sunday and warned the family not to hold a funeral, Mr. Makhmalbaf wrote.
In some parts of Tehran, protesters pushed the police back, hurling rocks and capturing several police cars and motorcycles, which they set on fire. Videos posted to the Internet showed scenes of mayhem, with trash bins burning and groups of protesters attacking Basij militia volunteers amid a din of screams.
One video showed a group of protesters setting an entire police station aflame in Tehran. Another showed people carrying off the body of a dead protester, chanting, “I’ll kill, I’ll kill the one who killed my brother.”
By late afternoon, coils of black smoke rose over central Tehran from dozens of street fires, and smaller groups of protesters continued to skirmish with police and Basij militia members. In the evening, loudspeakers in Imam Hussein Square, where most of the clashes took place, announced that gatherings of more than three people were banned, witnesses said.
There were scattered reports of police officers surrendering, or refusing to fight. Several videos posted on the Internet show officers holding up their helmets and walking away from the melee, as protesters pat them on the back in appreciation. In one photograph, a police officer can be seen holding his arms up and wearing a bright green headband, the signature color of the opposition movement.
The Tehran police denied firing on protesters and in an official statement late Sunday said five people had been killed “in suspicious ways.”
Ahmadreza Radan, deputy commander of state security forces in Tehran, said dozens of police officers had been injured and “some were killed,” the semiofficial news agency ISNA reported.
Protests and clashes also broke out in the cities of Isfahan, Mashhad, Shiraz, Arak, Tabriz, Najafabad, Babol, Ardebil and Orumieh, opposition Web sites said.
Foreign journalists have been banned from covering the protests, and the reports could not be independently verified.
If the 10 deaths are confirmed, it would be the highest toll since the summer, when huge crowds took to the streets to protest what they said was rampant fraud in the presidential election won by Mahmoud Ahmadinejad.
The White House condemned what it called the “unjust suppression” of civilians by the Iranian government on Sunday.
“Hope and history are on the side of those who peacefully seek their universal rights, and so is the United States,” said Mike Hammer, a spokesman for the National Security Council.
The turmoil revealed an opposition movement that is becoming bolder and more direct in its challenge to Iran’s governing authorities. Protesters deliberately blended their political message with the day’s religious one on Sunday, alternating antigovernment slogans with ancient cries of mourning for Imam Hussein.
“This is the month of blood, Yazid will fall,” the protesters shouted, equating Ayatollah Khamenei with Yazid, the ruler who ordered Imam Hussein’s killing.
The protests may have received a boost from the death last week of Grand Ayatollah Hossein Ali Montazeri, a patriarch of Iran’s Islamic Revolution who became a fierce critic of the country’s leaders, especially in recent months. His memorials have brought out not only the young activists and students who have dominated the protests in recent months, but also older and more conservative people, who revered him for reasons of faith as well as politics.
Sunday was the seventh day since his death, an important marker in Shiite mourning rituals. Late Sunday, the authorities declared martial law in the city of Najafabad, Ayatollah Montazeri’s hometown, the Jaras Web site reported.
The government crackdowns on mourning ceremonies in the past week provoked many people in the more traditional neighborhoods of south Tehran as earlier clashes did not, some residents said.
“People in my neighborhood have been going to the Ashura rituals every night with green fabric for the first time,” said Hamid, 33, a laborer who lives in the southern Tehran neighborhood of Shahreh-Ray and declined to give his last name. “They have been politicized recently, because of the suppression this month.”
Yet few protesters expected the scale of the bloodshed that broke out on Sunday. The memory of Imam Hussein is so potent among Shiites that killing for any reason is strictly forbidden on Ashura, and Iranian leaders have always tried to avoid violence or even state executions during a two-month period surrounding the holiday.
“Ashura is a very symbolic day in our culture, and it revives the notion that the innocents were killed by a villain,” said Fatemeh Haghighatjoo, a former member of the Iranian Parliament who is a visiting scholar at the University of Massachusetts, Boston. “Killing people on Ashura shows how far Khamenei is willing to go to suppress the protests.”
In another sign of the breadth of the crackdown, security forces on Sunday raided the offices of a clerical association in the holy city of Qum that has supported the opposition since the June election, the Jaras Web site reported. Guards surrounded the house, and members of the association and their families — who had gathered inside the association’s headquarters for an Ashura mourning ceremony — were not allowed to leave, the site reported.
Mr. Radan, the police deputy commander, said that only one of the protesters killed in Tehran had been shot. Two were run over by cars and one was thrown from a bridge, he said.
But a doctor working at Najmieh Hospital in Tehran said Sunday night that the hospital had performed 17 operations on people with gunshot wounds. They were treating 60 people with serious head injuries, including three who were in critical condition, said the doctor, who spoke on the condition of anonymity for fear of repercussions.