CAIRO—A bomb exploded at Cairo’s main Coptic Christian cathedral compound on Sunday morning, killing at least 25 people and wounding another 49, in the largest attack on a Christian house of worship in Egypt since 2011.

The blast went off on the women’s side of the worshiping hall in the small church of St. Peter and St. Paul, attached to the Coptic cathedral in the capital’s Abassyia district, state media reported.

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