Egyptian policemen stand guard at the scene of a powerful explosion believed to be a car bomb at a police headquarters building that killed at least a dozen people, wounded more than 100, and left scores buried under the rubble, in the Nile Delta city of Mansoura, 110 kilometers (70 miles) north of Cairo, Egypt, Tuesday, Dec. 24, 2013. The country’s interim government accused the Muslim Brotherhood of orchestrating the attack, branding it a “terrorist organization.” No one immediately claimed responsibility for the bombing, which came a day after an al-Qaida-inspired group called on police and army personnel to desert or face death at the hands of its fighters. (AP Photo/Ahmed Ashraf)