Egyptian witnesses say masked men blocked trains at a central Cairo subway station, standing on tracks and getting into fistfights with some waiting passengers who tried to stop them. Meanwhile, protesters locked shut the doors of the main administrative building for state services just outside the station at Tahrir Square, while others blocked traffic at a main bridge on the other side of town near the presidential palace by standing in the road.

Demonstrators have been sleeping in tents at Tahrir since mid-November to protest policies of Islamist President Mohammed Morsi.

The action comes on the second anniversary of the ouster of Egypt's longtime autocrat Hosni Mubarak, deposed in a popular uprising.