FREETOWN, Sierra Leone — Sierra Leone’s president declared a nationwide curfew Sunday after gunmen attacked the military’s main and largest barracks in the West African nation’s capital and then overran detention centers, including a major prison.

       The attack raised fears of a breakdown of order amid a surge of coups in the region.

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       The detention centers, including the Pademba Road Prisons — holding more than 2,000 inmates — were attacked just as security forces fought to restore calm during sustained shootouts at the Wilberforce military barracks, according to Information Minister Chernor Bah.