WASHINGTON — Iran's government smothered Tehran and other major cities with security forces Thursday, overwhelming opposition protesters who gathered in small groups despite threats of repression on the 31st anniversary of Iran's Islamic Revolution.
State security forces attacked one of President Mahmoud Ahmadinejad's political opponents, former parliament speaker Mehdi Karroubi, and the wife of another, Mir Hossein Mousavi, according to opposition Web sites and other accounts that filtered out of the country despite government efforts to restrict and monitor Internet traffic.
Video accounts posted on YouTube, Twitter, Facebook and other social networking sites showed helmeted riot police using tear gas and batons to prevent large crowds from gathering.
One widely circulated video showed a member of the riot police choking and punching a shirtless man. Before the 20-second clip ends, a woman dressed in traditional black walks up, points an accusatory finger at the policeman and remonstrates with him.
The show of force seemed intended to demonstrate, both to Iranians and to the West, that the leaders of Iran's Islamic Republic are firmly in charge eight months after a disputed presidential election sparked the country's deepest political crisis since 1979.
With most foreign journalists barred from Iran, and Internet and other media tightly controlled, it's not possible to independently verify some of the accounts.
However, one of Karroubi's sons, Mohammed Taghi Karroubi, told the BBC Persian service that his father was sprayed in the face with tear gas and hit with a stone when he tried to join the protesters.
Mousavi's wife, Zahra Rahnavard, who campaigned last year with her husband, was beaten and kicked by plainclothes police, according to Kaleme, an opposition Web site.
The crushing display of force appeared to be a setback for Iran's "green movement," as the protesters are known. Yet the movement, named after the color used in Mousavi's campaign, has proved resilient, and video clips showed opposition crowds gathered not just in Tehran, but also in other major cities. In Isfahan, crowds were shown shouting "Death to (Supreme Leader Ali) Khamanei."
Ahmadinejad, meanwhile, spoke to a huge pro-government throng in Tehran's Azadi, or Freedom, Square. In the past, the government has bused thousands of its supporters into Tehran from the provinces, often providing free meals and other enticements.
Ahmadinejad also used the symbolic occasion to claim that Iran is now a "nuclear state," a boast that U.S. government and private experts called wildly exaggerated.
The Iranian president announced that Iran's nuclear scientists have succeeded in enriching uranium to 20 percent purity, closer to the 80 percent enrichment needed to make a nuclear weapon.
"Iran has made a series of statements that are far more political than they are. They're based on politics, not on physics," responded White House spokesman Robert Gibbs.
"The Iranian nuclear program has undergone a series of problems throughout the year," Gibbs said. "We do not believe they have the capability to enrich to the degree to which they now say they are enriching."
David Albright, an expert on Iran's nuclear program at the Institute for Science and International Security, said earlier this week that Iran has the technical ability to produce uranium enriched to near 20 percent. He cast doubt, however, on Iran's claim that it could begin doing so immediately.
While Thursday's protests against Ahmadinejad were smaller than predicted, senior U.S. officials say that the government and its opponents are in for a long-term standoff, with neither side able to prevail.
Mehdi Noorbaksh, an associate professor at Harrisburg University in Pennsylvania, said Iran's opposition is engaged in "a war of attrition," hoping to encourage defections of Iranian diplomats and middle-ranking members of the Islamic Revolutionary Guard Corps who are unhappy with the government.
"I'm very positive," said Noorbaksh, whose father-in-law, Ebrahim Yazdi, was foreign minister in the interim government that followed the Shah's fall in 1979 and has been in jail since late December. "It is a long struggle."
(Steven Thomma contributed to this article.)
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