Syria's Interior Ministry says the sleeper cell behind a deadly church explosion near Damascus belonged to the Islamic State group.

Syrian authorities on Monday announced arrests over a suicide blast targeting a church blamed on the Islamic State group, as President Ahmed al-Sharaa vowed those involved in the "heinous" attack would face justice.

Syrian Christians were struggling on Monday to understand why their community was targeted in a suicide attack and whether they can rely on the Islamist-led government's assurances of protection.Syria's health ministry said the toll from Sunday's attack on the Mar Elias Church in the Dweila neighborhood had risen to 25 dead and more than 60 wounded.