Official Iranian claims that Mahmoud Ahmadinejad had won Friday's presidential elections by a landslide sparked the heaviest unrest in the capital for years on Saturday, with reports of three protesters killed by police. There was confusion late Saturday night over whether Mir Hossein Mousavi, the main election challenger who had earlier rejected the results as fraudulent, had been arrested. Some reports said he had been detained en route to see Supreme Leader Ali Khamenei, but amid a widespread official communications clampdown, no confirmation was available at press time. Hashemi Rafsanjani, a former president and head of the Expediency Council - Iran's top political arbitration body, resigned from his office, reportedly in protest over the results. Mousavi's supporters clashed with police and set up barricades of burning tires throughout the day. By nightfall, cell phone service appeared to have been cut in Teheran, rioting continued and fires were burning on the streets. Helmeted police on foot and others on buzzing motorcycles chased bands of protesters. Officers beat protesters with swift blows from their truncheons and kicks with their boots. Some of the demonstrators grouped together to charge back at police, hurling stones. Plumes of dark smoke streaked over the city. Protesters also torched an empty bus, engulfing it in flames on a Teheran street. Ahmadinejad, in a nationally televised victory speech, accused the foreign media of coverage that harms the Iranian people and promised "a bright and glorious future" for Iran. Several hundred demonstrators - many wearing the trademark green colors of pro-reform candidate Mousavi's campaign - chanted "the government lied to the people" and gathered near the Interior Ministry, as the final results were announced. It gave 62.6 percent of the vote to Ahmadinejad and 33.75% to Mousavi - a former prime minister who has become the hero of a youth-driven movement seeking greater liberties and a gentler face for Iran abroad. Turnout was a record 85 percent of the 46.2 million eligible voters. Sara Hasani, a young Iranian who led Mousavi's green campaign in her local neighborhood, alleged that "they [the government] robbed us of Mousavi's victory." It was "simply not possible" that Ahmadinejad had won, she said. "They cannot give us hope and take it away from the people. It appears Ahmadinejad has successfully manipulated the campaign scene better than we thought. Our votes are meaningless. It's a cruel joke," she said. But Khamenei closed the door on any chance he could use his limitless powers to intervene in the disputes. In a message on state TV, he urged the nation to unite behind Ahmadinejad, calling the result a "divine assessment." But Mousavi rejected the result as rigged and urged his supporters to resist a government of "lies and dictatorship." "I'm warning that I won't surrender to this manipulation," said a statement on Mousavi's Web site. "The outcome of what we've seen from the performance of officials ... is nothing but shaking the pillars of the Islamic Republic of Iran's sacred system and governance of lies and dictatorship." Mousavi warned "people won't respect those who take power through fraud." Mousavi appealed directly to Khamenei to intervene and stop what he said were violations of the law. Khamenei, who is not elected, holds ultimate political authority in Iran and controls all major policy decisions. Mousavi's campaign headquarters urged people to show restraint. An apparently skeptical Secretary of State Hillary Rodham Clinton said the US hopes the outcome of the election reflects the "genuine will and desire" of the Iranian people. White House press secretary Robert Gibbs said the US administration is paying close attention to reports of alleged election irregularities. The clashes in central Teheran were the more serious disturbances in the capital since student-led protests in 1999. They showed the potential for the showdown to spill over into further violence and challenges to the Islamic establishment. The demonstrations began Saturday morning shortly before the government announced the final results. Protesters set fire to tires outside the Interior Ministry and anti-riot police fought back with clubs and smashed cars. An Associated Press photographer saw a plainclothes security official beating a woman with his truncheon. Italian state TV RAI said one of its crews was caught in the clashes in front of Mousavi's headquarters. Their Iranian interpreter was beaten with clubs by riot police and officers confiscated the cameraman's tapes, the station said. On another main street of Tehran, some 300 young people blocked the avenue by forming a human chain and chanted "Ahmadi, shame on you. Leave the government alone." There were also protests in the southern city of Ahvaz in the oil-rich province of Khuzestan, where Mousavi supporters shouted, "Mousavi, take our votes back!" witnesses said. It was not clear how many Iranians were even aware of Mousavi's claims of fraud. Communications disruptions began in the later hours of voting Friday, suggesting an information clampdown. State television and radio only broadcast the Interior Ministry's vote count and not Mousavi's midnight news conference. After night fell, Teheran's cell phone network appeared to be down. When users tried to call cell phones, a message appeared on their phones saying "error in connection." Nationwide, the text messaging system remained down Saturday and pro-Mousavi Web sites were blocked or difficult to access. It was also difficult to access social networking sites such as Facebook, which Mousavi's campaign used to galvanize supporters. Ahmadinejad called on the public to respect the vote and attacked the foreign media's coverage. "All political and propaganda machines abroad and sections inside the country have been mobilized against the nation," he said in a televised address. "They have launched the heaviest propaganda and psychological war against the Iranian nation. Many global networks continuously worked, employing very complicated methods, that work against our nation and arranged a full-fledged battle against us." Without mentioning the unrest on the streets, Ahmadinejad proclaimed that "a new era has begun in the history of the Iranian nation... A bright and glorious future is ahead ... I invite everyone to join me in constructing Iran," he said. Interior Minister Sadeq Mahsouli, who supervised the elections and heads the nation's police forces, warned people not to join any "unauthorized gatherings." The powerful Revolutionary Guard cautioned Wednesday it would crush any "revolution" against the Islamic regime by Mousavi's "green movement." Police stormed the headquarters of Iran's largest reformist party and arrested several top reformist leaders, said political activists close to the party. The election outcome will not sharply alter Iran's main policies or sway major decisions, such as possible talks with Washington or nuclear policies. Those crucial issues rest with the ruling clerics headed by Khamenei. But the election focused on what the office can influence: boosting Iran's sinking economy, pressing for greater media and political freedoms, and being Iran's main envoy to the world. Iran does not allow international election monitors. During the 2005 election, when Ahmadinejad won the presidency, there were some allegations of vote-rigging from losers, but the claims were never investigated. Allegations are widespread that foul play and sabotage impacted the final outcome. Some Iranians are asserting that there were insufficient polling stations and shortages of ballot papers in pro-Mousavi neighborhoods, that voters were preventing from casting their ballots by the authorities, and that ominous threats were issued that the regime would lash out if Ahmadinejad were to lose. The "green" Mousavi campaign network was aware of such dangers ahead of Friday's polling and even warned supporters to cast their votes in schools rather than mosques. But the word from his camp is that it was also hamstrung by government interference in his supporters' Internet communications, and that his representatives were not allowed to monitor the voting in some areas. To their misfortune, it is being charged, they were left outside to watch Ahmadinejad's officials direct proceedings. There are also reports of Iranians being locked out of polling booths in certain provinces while poorer voters, widely regarded as the incumbent president's largest and most dependable group of supporters, lined up with ease to cast their ballots at local mosques. There were even rumors that pens provided at polling stations were filled with disappearing ink. Supporters of Mousavi and fellow reformist challenger Mahdi Karroubi were urged to bring their own. Interior Minister Mahsouli disputed that there were problems, however, and Khamenei urged voters, as he cast his ballot Friday, "Don't pay attention to the rumors." "Deep down I knew Ahmadinejad was promised another four years by the Supreme Leader, but I didn't want to believe it," added a young man who said he had been prevented from voting because the authorities "ran out of ballots." "Now when I look at Ahmadinejad's behavior throughout his campaign," he went on, "it is obvious that he was already preparing for his next term. His last three weeks, for example, have been filled with diplomatic meetings in Pakistan, Iraq, Afghanistan and Turkey. We all should have known, the dictator is here to stay." Mousavi favors trying to repair ties to the US and economic liberalization. His supporters said Saturday they fear Ahmadinejad, who publicly clashed with his rival over domestic and international issues in a campaign remarkable for the candidates' personal feuding and the intensity of their respective supporters' street rallies, would now move to unseat reformist figures from positions of influence.