BEIRUT, Lebanon — Iran’s beleaguered opposition movement struggled to reassert itself on Wednesday, as tens of thousands of protesters braved police beatings and clouds of tear gas on the sidelines of a major, government-sponsored anti-American rally.
The protests — in Tehran and other cities — were the opposition’s largest street showing in almost two months and came on the 30th anniversary of the takeover of the United States Embassy in Iran, an event that was a crucible for both Iran and the United States. Although a huge force of police officers beat back and scattered many of them, the protesters took heart at their ability to openly challenge the government despite a stream of warnings from all levels of Iran’s conservative establishment.
Even some government authorities seemed to grudgingly concede that the opposition had — for the first time — disrupted the annual anti-American rally. The official IRNA news agency reported in midafternoon that “rioters,” many wearing the opposition’s signature green color, had gathered in front of its offices on Valiasr Street chanting “Death to the dictator” and other antigovernment slogans.
At the same time, a new theme emerged, with many protesters declaring their impatience with President Obama’s policy of dialogue with the Iranian government. Many could be heard chanting, “Obama, Obama — either you’re with them or you’re with us,” witnesses said.
Mr. Obama released his own statement on Wednesday to mark the anniversary of the embassy takeover, repeating his appeals to move beyond the two countries’ mutual distrust. The statement expressed sympathy for Iran’s opposition movement and suggested that time was running out on a United Nations-backed plan aimed at averting a showdown over Iran’s nuclear ambitions.
“The world continues to bear witness to their powerful calls for justice and their courageous pursuit of universal rights,” the statement said of the Iranian people. “It is time for the Iranian government to decide whether it wants to focus on the past, or whether it will make the choices that will open the door to greater opportunity, prosperity, and justice for its people.”
Protesters openly flouted the day’s official anti-American message, with about 1,000 people gathering outside the Russian Embassy in Tehran and chanting, “The real den of spies is the Russian Embassy.”
The American Embassy has been called the “den of spies” in Iran for decades. But many opposition supporters were angered by Russia’s early acceptance of Mahmoud Ahmadinejad’s disputed victory in Iran’s presidential election in June.
On Tuesday, Iran’s supreme leader, Ayatollah Ali Khamenei, gave an angry speech accusing the United States of dictating the terms of the nuclear deal, and suggested that Mr. Obama was no different from his predecessor.
There were reports of several dozen arrests in Wednesday’s protests, including some outside Tehran, and many injuries. The reformist cleric Mehdi Karroubi, who has become the government’s most outspoken critic, narrowly avoided injury when pro-government forces fired a tear gas cylinder at him as he marched with protesters in Tehran, according to Radio Farda, an American-backed station. Two of his guards leapt to defend him and were hospitalized for their wounds, the station reported.
Mir Hussein Moussavi, who was Mr. Ahmadinejad’s main challenger in the election, was prevented by security officers from attending the protests, Radio Farda reported.
Over all, the police appeared to have fought back protesters more aggressively than they did in September, when opposition supporters in much larger numbers virtually hijacked a state-sponsored rally known as Jerusalem Day.
The protest turnout on Wednesday may also have been limited by the fact that it took place on a workday, unlike the Jerusalem Day protest. Still, starting early in the morning, the streets of central Tehran were lined with police officers and Basij militia members, witnesses said. In the subways, officers singled out people wearing green armbands, bracelets or head scarves and ripped them off.
One young man who had been leading antigovernment chants in Valiasr Square summed up the day’s events: “One day we come out and it’s our day, another day they suppress us. Today, we did not get to have our say, but it was good enough that we brought them out onto the streets.”
Still, the day was a tonic to the opposition, which has struggled to maintain its momentum since the June election set off the country’s worst domestic unrest since the 1979 Islamic Revolution. The authorities have brutally suppressed the movement in recent months through a combination of arrests, show trials and intimidation. Many leading reformist figures remain in jail, and while some detainees have been released, the government arrests more critics every week.
The protests in Tehran began in Haft-e-Tir Square. Many demonstrators wore surgical masks in anticipation of tear gas. As their numbers grew, police officers and Basij militia members fired tear gas and lunged periodically into the crowd to beat or arrest protesters.
A disorderly march began, moving westward toward Valiasr Square, the scene of many earlier protests. The government’s official rally was taking place on a parallel route to the south, and a deployment of police officers and militia men prevented protesters from reaching it. By mid-afternoon, both demonstrations appeared to be ending.
Many protesters seemed acutely conscious of the government’s vulnerability, after a week during which Mr. Ahmadinejad often seemed to be alone in his support for concluding a nuclear deal with the West.
“They should get rid of all this ‘death to, death to’ — death to what?” said a middle-aged woman marching with her two daughters. “On the one hand they shout ‘Death to America’ and on the other hand they go and make deals with them.”
The anniversary of the embassy takeover underscored a broader unease about relations with the West. The day has long been a touchstone for Iran’s revolutionaries, but Mr. Obama’s outreach has complicated the state’s reflexive anti-Americanism. One of Iran’s leading reformist voices, Grand Ayatollah Hossein Ali Montazeri, surprised many of his compatriots by declaring on Tuesday that the seizure of the embassy in 1979 was “not the right thing to do.”
Mr. Ahmadinejad himself has argued that Iran has tamed the West’s arrogance and should now agree to the proposed nuclear deal, under which Iran’s uranium would be shipped abroad for processing and eventually returned in the form of fuel rods for a reactor to make medical isotopes.
But his political enemies, both conservative and reformist, have seized on an opportunity to humiliate him, and have assailed the nuclear plan as a surrender to the West — a strategy he used against them in years past.