A protester collects stones to use against riot police during clashes near Qasr el-Nil bridge, in Cairo January 29, 2013. Egypt's army chief said political unrest was pushing the state to the brink of collapse - a stark warning from the institution that ran the country until last year as Cairo's first freely elected leader struggles to curb bloody street violence. REUTERS/Asmaa Waguih (EGYPT - Tags: POLITICS CIVIL UNREST)