"I collapsed from exhaustion, from the heat, from hard work, from antibiotics I am taking for a knee operation," Former Premier Silvio Berlusconi said after his near collapse during a speech in northern Italy. "They found something in the electrocardiogram, various extra systoles," said Berlusconi, looking a bit drawn. Berlusconi nearly collapsed at a podium during an emotional speech to political supporters in northern Italy on Sunday, and aides rushed to keep him from falling over. The 70-year-old media mogul later blamed the incident in Montecatini Terme, a spa resort, on exhaustion and said he was being hospitalized for tests. After flying to one of his villas near Milan by helicopter, Berlusconi told reporters: "I feel well" but that he was going to spend 24 hours in observation at a Milan hospital as a precaution. A systole is the contraction of the heart by which blood is forced onward for circulation. After some 40 minutes of railing against Premier Romano Prodi's center-left government, Berlusconi, who leads the conservative opposition, suddenly started speaking slowly, looked weak and told a partisan crowd in the spa resort of Montecatini Terme: "And now, excuse me, emotion is getting the better of me, and I ..." His voice trailed off, and he gripped the podium for support as he leaned back. "Silvio Berlusconi had a strong drop in blood pressure, he's much better now," his spokesman, Paolo Bonaiuti, told RAI state TV. Prodi told reporters that he had spoken to a senior Berlusconi aide, Gianni Letta, offering his best wishes for recovery, and was assured that the opposition leader had suffered a temporary ailment. Bonaiuti told Sky TG24 TV, which covered the speech live, "The worst is over" and that Berlusconi was "sorry he couldn't finish the speech," the spokesman said. About a half hour after he fell ill, Berlusconi walked out of the hall in Montecatini Terme, to a waiting car. He looked pale as he waved to supporters of his Forza Italia party. A Berlusconi supporter, former Chamber of Deputies speaker Irene Pivetti, told the crowd that Berlusconi had "fallen ill because of the tension, because of the emotion" of the speech. Berlusconi's personal physician, Umberto Scapagnini, told Sky TG24 that Berlusconi was examined by a cardiologist before he left the rally site. During the speech, Berlusconi expressed anger over the center-left's victory in elections in April, which saw him lose power to Prodi and his allies. He pounded his hand on the lectern and shouted at times. The media magnate's anger was fueled by a claim in an Italian documentary that Berlusconi's conservative coalition tried to rig the election through an alleged fraudulent count of thousands of blank ballots . An Italian prosecutor has opened an investigation into the claim, which touched off a political storm. Berlusconi told his supporters that his coalition had asked for a recount but contended that the parliamentary electoral committee, controlled by the governing coalition, was thwarting the request. "We haven't been able to check not even a single ballot," the ex-premier said, his voice rising. His former interior minister, who oversaw the vote process, has called the accusations as false and libelous, and on Sunday, Berlusconi joined some of his conservative allies in counterclaiming that if there were fraud, it would have come at the hands of the center-left.