Egyptian riot police fired tear gas and clashed all day Thursday with dozens of protesters as they tried to tear down a cement wall built to prevent demonstrators from reaching the parliament and the Cabinet building in central Cairo. Some in the crowd threw rocks and Molotov cocktails.

The violence came on the eve of the second anniversary of Egypt's uprising that toppled longtime authoritarian President Hosni Mubarak. Three weeks of mass protests that erupted on Jan. 25, 2011, eventually forced Mubarak out of office.

Since then, Egypt has undergone a tumultuous transition under the interim leadership of military generals until the election last June of Mohammed Morsi of the Muslim Brotherhood group. His first six months in office were marked by political tensions, street clashes, and an economic crunch that sapped his popularity.