Four people, including an Egyptian female journalist, were killed in Cairo as police clashed with protesters demonstrating against ex-army chief Abdel Fattah el-Sisi's presidency bid, a security official said. The violence erupted as supporters of deposed president Mohamed Morsi took to the streets of Cairo, Alexandria and other cities on Friday to vent their anger at Sisi, who overthrew the Islamist nine months ago. Sisi, who was also defence minister and deputy prime minister, announced his resignation on Wednesday to enable him to stand in the election. Al Jazeera's Charles Stratford reports.