TEHRAN- Iran's top legislative body on Tuesday ruled out annulling a disputed presidential poll that has prompted the biggest street protests since the 1979 Islamic revolution but said it was prepared for a partial recount.

In what appeared to be a first concession by authorities to the protest movement, the 12-man Guardian Council said it was ready to re-tally votes in the poll in which hard-line President Mahmoud Ahmadinejad was declared the runaway winner.

But the powerful Council rejected reformist calls to annul Friday's election that set off swift-moving political turmoil, riveting attention on the world's fifth biggest oil exporter which is locked in a nuclear dispute with the West.

Supporters of Mirhossein Mousavi, outraged at his defeat in what they viewed as a stolen election, planned another rally on Tuesday, even though seven people were killed on Monday on the fringes of a huge march through the streets of Tehran.

Mousavi urged people not to attend the banned rally at Vali-ye Asr Square in Tehran to protect lives saying it was canceled, but it was not clear if the call was heeded.

Supporters posted defiant messages on Twitter, calling for the demonstration to go ahead and offering security updates.

State television showed live pictures of what it said were Ahmadinejad supporters gathering at the Vali-ye Asr Square, showing thousands of people, some waving Iranian flags, possibly setting the scene for more confrontation.

Iranian state television said on Tuesday the main agents in post-election unrest had been arrested with explosives and guns. It gave no further details in a breaking news headline.

Further protests, especially if they are maintained on the same scale, would be a direct challenge to the authorities who have kept a tight grip on dissent since the 1979 overthrow of the U.S.-backed shah after months of demonstrations.

Illustrating Iran's sensitivity to how the world views the heightened tensions, authorities on Tuesday banned foreign media journalists from leaving their offices to cover street protests.

No journalist has permission to report or film or take pictures in the city, a Culture Ministry official told Reuters.

The United States and its European allies have been trying to persuade Iran to halt nuclear work that could be used to make an atomic bomb. Iran denies it seeks atomic weapons and says it wants nuclear energy only to generate electricity.

U.S. President Barack Obama, who has sought to reach out to Iran asking its leadership to unclench its fist, said he was deeply troubled by the post-election violence and that protesters who had taken to the streets had inspired the world.

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A spokesman for the Council, which groups clerics and Islamic law experts as a constitutional watchdog, said only that it was ready to recount the disputed ballot boxes claimed by some candidates, in the presence of their representatives.

It is possible that there may be some changes in the tally after the recount, spokesman Abbasali Kadkhodai said. Based on the law, the demand of those candidates for the cancellation of the vote, this cannot be considered, he told state television.

Despite protests and upheaval in Iran, Ahmadinejad was in Russia for SCO talks on Tuesday on his first foreign trip since official results showed he secured a second four-year term.

The Shanghai Cooperation Organization (SCO), which includes Russia and China, congratulated Ahmadinejad on his win.

Iran's English-language Press TV said seven people were killed and several wounded at the end of Monday's rally -- a mainly peaceful gathering attended by many tens of thousands -- when thugs tried to attack a military post in central Tehran.

An Iranian photographer at the scene had said Islamic militiamen opened fire when people in the crowd attacked a post of the Basij religious militia. He said one person was killed and many wounded in the shooting.

The Basij militia is a volunteer paramilitary force fiercely loyal to Supreme Leader Ayatollah Ali Khamenei who has the final say on all matters of state and who replaced revolutionary leader Ayatollah Ruhollah Khomeini when he died 20 years ago.

During the past three days of violence, police have accused bandits of setting buses on fire, breaking windows of banks and other buildings, and damaging public property.

Iran's influential speaker of parliament Ali Larijani, a conservative who has been critical of Ahmadinejad in the past, condemned Sunday's attack on students at Tehran University which they blamed on the Basij militia and plainclothes police.

They (attackers) have attacked dormitories and brutally broken legs, heads, arms and threw some of the students out of the windows, Mousavi said, according to his website.

There have been widespread arrests across the country since the election protests broke out. The ISNA news agency said on Tuesday around 100 people were arrested in unrest near a university in the southern city of Shiraz.

Leading Iranian reformist Mohammad Ali Abtahi, a former vice-president who backed pro-reform candidate Mehdi Karoubi in the election, was arrested early on Tuesday, his office said.

Gunfire was heard in districts of northern Tehran late on Monday and residents said there were peaceful pro-Mousavi protests in the cities of Rasht, Orumiyeh, Zahedan, and Tabriz.

Iran's security forces have at times fired into the air and used batons to beat protesters who pelted police with stones. (Writing by Peter Millership)

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