TEHRAN, Iran -- Police used tear gas and batons Tuesday to disperse resurgent anti-government protesters demanding the release of opposition leaders in the biggest clashes in Iran's capital since demonstrators stormed back to the streets two weeks ago, witnesses and opposition websites said.
The recent return of skirmishes in the heart of Tehran -- absent for more than a year after relentless crackdowns -- borrow some raw inspiration from uprisings in the neighboring Arab world. But it also reflects a possible miscalculation by authorities who sought to silence opposition leaders but instead gave their supporters a new rallying point.
Reports by family members and opposition websites claim the two most prominent anti-government figures, Mir Hossein Mousavi and Mahdi Karroubi, have been moved from house arrest to full-time detention along with their wives. Iranian authorities deny the reports, but the two opposition leaders have not been seen in public or posted statements on their websites in more than a week.
The jail-like controls, opposition groups say, was payback for embarrassing Iran's leaders by urging demonstrations Feb. 14 to show support for the toppling of regimes in Tunisia and Egypt -- rebellions Iran's ruling system had already praised.
The apparent goal was to discourage more protests by muzzling the former parliament speaker Karroubi and Mousavi, who claims he was the rightful winner of the 2009 election and that President Mahmoud Ahmadinejad was re-elected through massive vote fraud. But it may have backfired and helped re-energize the opposition movement and restore the rebel image of the two anti-government leaders, whose clout had waned considerably and was mostly limited to proclamations on websites.
Protesters rallied at several points in the capital, chanting "Death to the dictator" and urging authorities to free Mousavi and Karroubi, according to the opposition kaleme.com website.
Witnesses said riot police charged on protesters in central Tehran to try to scatter crowds. Some police took swipes at cars whose drivers were believed to be honking their horns in support of the demonstrators. There were no reports of injuries, but opposition websites said several people were arrested.
Kalame said the violence by security forces against protesters was "heavy and unprecedented." It said gunfire was heard during the clashes.
Reports cannot be verified independently since Iranian authorities have banned media from covering opposition protests and other events. Opposition websites have called for another day of protests in Iran on March 8.
Mousavi and Karroubi were put under house arrest after they called for the Feb. 14 rally, the largest in more than a year following a relentless crackdown by Iranian authorities. Clashes between protesters and security forces during the demonstrations killed two and wounded dozens.
Both Mousavi and Karroubi -- who also ran in the June 2009 election -- have been under increasing pressure from authorities who crushed street protests by their supporters.
Iran's leadership has rejected calls by hard-liners to bring the two to trial on anti-state charges, fearing that it could serve as a rallying point for opposition supporters. The current claims about their detentions, however, could also help to re-energize opposition forces.
Foreign Ministry spokesman Ramin Mehmanparast said Iran will not respond to international questions about the whereabouts of the two, adding that the country considers the matter a "completely domestic" affair.
The semiofficial news agency ISNA quoted state prosecutor Gholam Hossein Mohseni Ejehei as saying the two were not detained but did not elaborate. On Monday, he said authorities have cut all outside contact with them as part of a campaign to silence dissent.
However, the opposition and their relatives said they are being held in a military garrison in Tehran.
There has been no independent confirmation of their location.
White House spokesman Jay Carney told reporters Monday: "We obviously find the detention of opposition leaders to be unacceptable and we call on them to be treated well and released."
Mehmanparast denounced outside pressures to clarify the status of the two opposition figures.
"The internal issues of our country are completely domestic and no country is and will be allowed to interfere in the internal affairs of our country," he told reporters.
Mehmanparast said any "issues relating to" Mousavi and Karroubi "will be dealt in the framework of law by judicial authorities."