Police fire tear gas at clashing protesters in Alexandria, Egypt, on the eve of a second day of polling on a controversial constitutional referendum.
Police Fire Tear Gas at Egyptian Protesters

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Riot police use tear gas to disperse protesters opposing Egyptian President Mohamed Morsi in Alexandria, Egypt, December 21, 2012.

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Protesters supporting Egyptian President Mohamed Morsi gesture as anti-Morsi protesters throw rocks at them during clashes in Alexandria, Egypt, December 21, 2012.

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Opponents of Egyptian President Mohamed Morsi clash with Islamist supporters of the president, unseen, as a cordon of riot police separates the groups in Alexandria, Egypt, December 21, 2012.

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Riot police try to prevent protesters supporting Egyptian President Mohamed Morsi from throwing rocks at anti-Morsi protesters during clashes in Alexandria, Egypt, December 21, 2012.