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Protesters run from tear gas during clashes with Egyptian riot police in Tahrir Square in Cairo, Egypt, Sunday, Nov. 20, 2011. Firing tear gas and rubber bullets, Egyptian riot police on Sunday clashed for a second day with thousands of rock-throwing protesters demanding that the ruling military quickly announce a date to hand over power to an elected government. (AP Photo)

Protesters run from tear gas during clashes with Egyptian riot police in Tahrir Square in Cairo, Egypt, Sunday, Nov. 20, 2011. Firing tear gas and rubber bullets, Egyptian riot police on Sunday clashed for a second day with thousands of rock-throwing protesters demanding that the ruling military quickly announce a date to hand over power to an elected government. (AP Photo)

Egypt protests in pictures

There has been a fresh wave of violent clashes between demonstrators and police in Tahrir Square, Cairo, amid calls for Field Marshal Hussein Tantawi to step down immediately in favour of an interim civilian council. Four days of protests has seen 38 people killed and scores injured.