TEHRAN — A pair of sprawling demonstrations here brought the capital of Iran virtually to a standstill on Monday, with followers of President Mahmoud Ahmadinejad and his main electoral challenger struggling to demonstrate their street following ahead of presidential elections on Friday.
The demonstrations were the largest gatherings here in more than a decade, veteran political observers said.
Iranian elections always bring a loosening of the rules on public speech and behavior, but many say this year’s election is different, in part because of the social crackdown of the past four years under Mr. Ahmadinejad.
“What’s happening now is more than what should happen before an election,” said Mashalah Shamsolvaezin, a political commentator and former director of several reformist newspapers. “This is an expression of protest and dissatisfaction by people. They are venting their frustration and feeling very powerful.”
Mr. Ahmadinejad’s campaign organized a huge rally in a prayer hall in central Tehran on Monday afternoon, where tens of thousands of chanting supporters gathered apparently in an effort to match the raucous outdoor rallies that are being held nightly by followers of Mir Hussein Moussavi, his leading challenger for the presidency.
But the president’s rally was overmatched in turn by a larger, simultaneous demonstration by Mr. Moussavi’s followers, who formed a human sea of people that blocked traffic for miles along one of Tehran’s main boulevards.
The rallies underscored the unusual passions being aroused by the campaign, in which the leading candidates have exchanged accusations that are extraordinarily fierce for Iranian politics. There have been scattered street clashes in recent days, but the police have generally not intervened, in part — analysts say — because they do not want to unleash protests by the unruly and mostly young crowds.
The rallies appear to have surprised and unsettled the authorities, and Iran’s supreme leader, Ayatollah Ali Khamenei, in a message broadcast on state television, warned against any further escalation.
“I don’t want to comment about people coming onto the streets, but they should not turn into confrontation or clashes between supporters of the candidates,” Ayatollah Khamenei said.
Monday’s rally by Mr. Moussavi’s supporters was motivated partly by anger at Mr. Ahmadinejad, whose campaign rescheduled its own rally in a way that displaced an event by Mr. Moussavi. He had planned to give a speech in the same prayer hall where Mr. Ahmadinejad appeared Monday. Instead, Mr. Moussavi’s followers gathered in a long chain running from the south of the capital to the north, most of them wearing sashes of green, his campaign’s signature color.
The campaign has included fierce spoken exchanges among the candidates, especially during the presidential debates of the past week, in which Mr. Ahmadinejad has accused leading figures of the 1979 revolution of corruption.
On Monday, Ali Akbar Hashemi Rafsanjani, a former two-time president and one of Mr. Ahmadinejad’s chief targets, defended himself for the first time.
“Unfortunately, the course of the election has become tainted with all sorts of lies and slanderous statements,” Mr. Rafsanjani said.
Although the harsh criticisms have shocked many Iranians, they seem to have played well with Mr. Ahmadinejad’s followers, who view them as a natural part of his populist campaign against the rich and the corrupt.
As it happened, the crowds at Mr. Ahmadinejad’s rally were so thick that he was not able to get through to the podium in time to speak, and many of his supporters left early. At the same time, not far away, thousands of Mr. Moussavi’s supporters crowded the streets, creating traffic jams so heavy that the blocked roads were full of people walking home through the stopped cars.
For weeks, Mr. Ahmadinejad’s opponents have been saying they are concerned that the government will rig the vote in his favor. On Monday, a group of Interior Ministry employees released a letter saying a senior cleric close to Mr. Ahmadinejad had authorized fixing the vote in his favor, several reformist Web sites reported."