By Jay Deshmukh
A suicide bomber meanwhile struck a key regime monument — the south Tehran mausoleum of revolutionary leader Ayatollah Ruhollah Khomenei, killing himself and wounding at least two people, state media reported.
The demonstrators braved tear gas and water cannon to assemble in Enghelab Square in the heart of the capital, witnesses said, as foreign media were again barred from covering the opposition event.
"The robocops beat us up badly," one protestor told AFP. "Men and women were beaten up… My whole body is bruised… They confiscated my camera."
Members of the Basij Islamic militia, which has been at the forefront of the regime's efforts to face down a week of protests against official results giving hardline incumbent Mahmoud Ahmadinejad a second four-year term, were again out in force.
However, protestors were catching Basijis on motorbikes and beating them, a witness said.
Riot police deployed to the rally venue chosen by opposition leaders after security chiefs threatened to deal harshly with any more protests against the official outcome of the June 12 election.
One of the rally organisers, the Combatant Clerics Assembly, had announced it was backing out after the authorities refused to grant authorisation.
The interior ministry said no rally would be permitted anywhere in the country and warned "those who violate this will be confronted according to the law."
On Friday, Iran's supreme leader Ayatollah Ali Khamenei demanded an end to the opposition's protests, warning the defeated candidates would be responsible any bloodshed beyond the seven deaths reported by state radio so far.
Amnesty International said it had reports of up to 10 deaths since the disturbances erupted.
The head of Iran's security council, Abbas Mohtaj, sent a specific warning to Ahmadinejad's main defeated challenger, moderate former premier Mir Hossein Mousavi.
"Your national duty tells you to refrain from provoking illegal gatherings," he wrote in the letter made public on Saturday.
"Should you provoke and call for these illegal rallies you will be responsible for the consequences."
Electoral watchdog the Guardians Council said it was ready to randomly recount up to 10 percent of ballot boxes from the election, state television reported.
It made its partial recount offer after meeting to study the 646 complaints of poll violations registered by the three defeated candidates — Mousavi, ex-parliament speaker Mehdi Karroubi and former Revolutionary Guards chief Mohsen Rezai.
Neither Mousavi nor Karroubi showed up at the meeting, Iran's Press TV reported, without saying why.
The Iranian capital has been rocked by daily demonstrations since the re-election of Ahmadinejad drew accusations by his defeated challengers of massive vote fraud.
Siding with Ahmadinejad in his first public appearance since the vote, Iran's supreme leader ruled out major fraud in the poll.
"The people have chosen whom they wanted," Khamenei said in a nationally broadcast address, referring to Ahmadinejad.
Mousavi has repeatedly demanded a re-run of the poll, denouncing the election as a "shameful fraud."
But Khamenei said there could be no doubting Ahmadinejad's re-election. "The legal mechanisms in our country do not allow cheating. How can one cheat with a margin of 11 million votes?" he asked.
US President Barack Obama warned Iran that the "world is watching" its actions.
"I'm very concerned based on some of the tenor and tone of the statements that have been made that the government of Iran recognise that the world is watching," the president said on US television.
Obama also attempted to debunk claims by some in the Iranian leadership that demonstrators were acting at the behest of the United States, which has had a history of antagonism with Iran since the 1979 Islamic revolution.
Senior US officials stressed that Washington was making strenuous efforts to avoid being drawn into the crisis in a way that could be used by the government against the demonstrators.
"The more the United States looks like they are going to interfere, the more it is going to be detrimental," said one official on condition of anonymity.
"This is not about us."
Other world powers and entities have also expressed concern about the post-election violence and widespread arrests, with EU leaders, the UN human rights body and Amnesty International urging Iran to respect the right to protest.
In the face of the regime's biggest crisis since the 1979 revolution overthrew the pro-Western shah, Iran's Islamic rulers have repeatedly lashed out at "meddling" by foreign powers.
