NEW : An opposition group demands that officials be sacked over the crackdown . The government has been accused of using excessive force against protesters and journalists in recent days as it tries to quell a wave of anti-government protests across Egypt. Police use tear gas and rubber bullets against protesters . Tahrir Square was the heart of the revolt against then-President Hosni Mubarak .
NEW : An opposition group demands that officials be sacked over the crackdown . Hundreds of people are treated at the scene and dozens end up in hospitals . Police use tear gas and rubber bullets against protesters . Tahrir Square was the heart of the revolt against then-President Hosni Mubarak .