CAIRO (Update 2) - Protesters clashed with military police in central Cairo on Friday after rumours spread that an anti-government activist was detained at a sit-in and badly beaten, in the worst violence since the start of Egypt's first free election in decades. Police fired in the air after dawn to try to disperse around 300 demonstrators who said they were angered by images posted online of the man - named as Abboudi Ibrahim - being supported by a crowd, his face badly bruised and eyes swollen and shut. The fighting continued and, by mid-morning, the area around the cabinet office and parliament was strewn with rubble as soldiers and men in plainclothes threw stones from the roofs of state buildings down on protesters, who hurled back rocks. Dozens of troops arrived, fired in the air and rounded up many protesters. The soldiers formed cordons to seal the area. A few demonstrators continued throwing stones at them but the streets were calmer by early afternoon. “Many protesters fell and were arrested by the army. There were no injuries from live ammunition, just sharp objects and rocks hurled from above,” said Yasser Higazie, a doctor in a makeshift clinic. Cars were set alight and part of a state building burned during the fighting. An assistant to Egypt's health minister said 15 people had been injured in the clashes, state newspaper al-Ahram's website reported. The sit-in outside cabinet was a leftover of far bigger protests last month in Tahrir Square and nearby streets that left dozens dead and overshadowed the build-up to the first parliamentary election since the overthrow of autocratic President Hosni Mubarak in February. Those protests turned streets near Tahrir Square into a battle zone for days, prompting the army-backed interim government to resign and the ruling generals to pledge to step aside by the end of June 2012. The cabinet is due on Sunday to hold a first full meeting since it was sworn in on Dec. 7 and plans to weigh new austerity measures to address a wider-than-expected budget deficit. State news agency MENA said activists were urging others to go to Cairo's landmark Tahrir Square for fresh protests. It said protesters later blocked one of the main entrances to Tahrir. Election turnout appeared relatively high again in the second round of voting on Wednesday and Thursday, which took in parts of greater Cairo, Ismailiya and Suez in the east, Aswan to the south and Nile Delta regions in the north. The leading group, the Muslim Brotherhood's Freedom and Justice Party (FJP), said it expected to hold onto its lead but that it was not clear whether its share of the vote would stay around the 40 per cent mark.