TEHRAN (Reuters/AFP) - Supreme Leader Ayatollah Ali Khamenei issued a strong warning on Friday to leaders of mass street protests against a disputed presidential election that they would be responsible for any bloodshed. His words appeared to hint at a future crackdown by authorities on rallies after the election a week ago, which Khamenei said was fairly won by Mahmoud Ahmadinejad and not rigged, as defeated candidate Mirhossein Mousavi alleges. Khamenei called for an end to the protests in his first address to the nation since the election results triggered the most widespread street demonstrations in the Islamic Republics 30-year history. If there is any bloodshed, leaders of the protests will be held directly responsible, the white-bearded cleric told huge crowds thronging Tehran University and surrounding streets for Friday prayers. Mousavis supporters had planned another demonstration on Saturday. But an ally of the defeated moderate candidate told Reuters after Khameneis speech that Mousavi had no plans to call a rally on Saturday (today) or Sunday (tomorrow). State media have reported seven or eight people killed in unrest since the election outcome was published on June 13, prompting Mousavis supporters to hold mass rallies in Tehran, with demonstrations reported in several Iranian cities. Scores of reformists have been arrested and authorities have cracked down on foreign and domestic media. London-based rights group Amnesty International said it believed 15 people had been killed in the violence. All the 15 killings are confirmed, she told AFP, adding that Amnesty was not yet sure whether they included five students. Khamenei called for calm in his country. The result of the election comes from the ballot box, not from the street, he said. Today the Iranian nation needs calm. Khamenei also attacked what he called interference by foreign powers who had questioned the result of the election, saying Irans enemies were trying to undermine the legitimacy of its Islamic establishment. American officials remarks about human rights and limitations on people are not acceptable because they have no idea about human rights after what they have done in Afghanistan and Iraq and other parts of the world, he said. If Mousavi supporters defy Khameneis explicit warning about further protests, they risk a severe response from security forces, which have so far not tried to prevent mass gatherings. Khamenei said defeated candidates were wrong to believe that by using street protests as a pressure tool, they can compel officials to accept their illegal demands. This would be the start of a dictatorship. Any election complaints should be raised through legal channels, he said, dismissing charges of fraud. Irans laws do not allow vote-rigging, especially at the level of 11 million, he said, referring to Ahmadinejads victory margin. State television coverage showed Ahmadinejad and defeated candidate Mohsen Rezaie attending the speech. The supreme leader, Irans ultimate authority, in theory stands above the factional fray, but Khamenei acknowledged that his views on foreign and domestic policy were closer to those of Ahmadinejad than to those of the hardline presidents foes. Thousands listened intently to Khameneis speech booming from loudspeakers outside Tehran University, at times cheering and chanting to voice their approval for his words. With this speech, the leader has finished all problems, one middle-aged cleric in the crowd said afterwards. The differences between the politicians will be resolved. Dont let the history of Iran be written with the pen of foreigners, one flyer said, reflecting official Iranian anger at international criticism of the post-election violence.