At least 15 people were killed when a suicide bomber blew himself up at the Mar Elias Church in the Dweila neighbourhood of Syria's capital Damascus, security sources said.
The incident on Sunday marks the first suicide bombing inside Damascus since Bashar al-Assad was toppled by an Islamist-led rebel insurgency in December.
Syria's interior ministry said the suicide bomber was a member of the Islamic State. He entered the church, opened fire and then detonated his explosive vest, the ministry added in a statement.
A security source, speaking on condition of anonymity, said two men were involved in the attack, including the one who blew himself up.
Syria's state news agency cited the health ministry as putting the preliminary casualty toll at nine dead and 13 injured.
A livestream from the site by Syria's civil defence, the White Helmets, showed scenes of destruction from within the church, including a bloodied floor and shattered church pews and masonry.
Syrian President Ahmed al-Sharaa, who led the offensive against Assad before taking over in January for a transitional phase, has repeatedly said he will protect minorities during his tenure.
