Scores hurt as violence flares in Cairo Stone-throwing protesters and army soldiers clashed in Cairo on Friday, sending political tensions soaring again less than three weeks before crucial presidential elections. Some 75 people were injured in the clashes near the defence ministry as troops and demonstrators pelted each other with rocks and the military used water cannons and teargas to try to disperse the crowds. Earlier the protesters cut through barbed wire barriers erected by the army to close off access to the ministry. Egyptian television showed footage of soldiers snatching a protester, beating him with metal sticks and tearing his clothes. "The people want to execute the field marshal," chanted the demonstrators, referring to Mohamed Hussein Tantawi, the defence minister and head of the military council which has been ruling the country in an interim capacity since last year's revolution. Army helicopters circled above as troops chased away the angry crowds from the road in front of the ministry and cleared away thousands of people who had massed in nearby Abbasiya square. The military then sealed off the area and deployed armoured personnel carriers on access roads, while protesters fled through side streets trying to evade troops and armed plainclothes men. The flare-up of violence in the run-up to country's first democratic presidential election highlights the volatility of Egyptian politics during a sensitive moment of what has been a messy and often violent transition to elected rule. The military, who have been overseeing the process, have promised to hand over power after the election, but the latest mayhem, if not quickly contained, could derail the process. The transition is already precarious with the ruling generals involved in a power struggle with the Muslim Brotherhood, the group which won parliamentary elections earlier this year. The Islamists say the generals want to be able to wield political influence beyond the end of the transition, and that their real intention is to continue to rule from behind the scenes The Brotherhood had called for a rally on Friday in Tahrir square in central Cairo, the latest in a series of such protests intended to put pressure on the ruling generals. Thousands of people also headed for Abbasiya "to make the army hear their voice." They included Islamists and secular activists who had been infuriated by the killing on Wednesday of 11 people when a sit-in near the ministry was attacked by unknown men armed with guns and knives. The assailants are believed to be paid thugs sent to break up the protest camp erected by hundreds of supporters of an ultraconservative Islamist leader who was disqualified as a presidential candidate. Political activists regularly accuse the military and police of using paid thugs to attack protests. The ruling military council had warned on Thursday of a tough response if anyone "approached" military installations. They affirmed their intention to guarantee the integrity of the election and said they would stick to their promise to leave power at the end of June.