At least 20 people were killed and 52 injured in an explosion by an apparent "Islamic State" suicide bomber at a church in the Syrian capital.

A blast rocked the Mar Elias Church in the Dweila neighborhood of Syria's capital, Damascus, on Sunday, according to witnesses.

One witness told Reuters news agency that a suicide bomber detonated himself inside the church. Syrian state TV also reported that a suicide bomb caused the blast.

Correspondents for the AFP news agency at the church said they saw shattered wood from fittings and pews and pools of blood on the ground.

In a post on X, Interior Minister Anas Khattab said: "These terrorist acts will not deter the Syrian state's efforts to achieve civil peace, nor will they deter Syrians from their choice to unite in the face of all those who seek to undermine their stability and security."

At least 20 reported dead

Security sources said at least 20 people were killed and 52 injured, with the suicide bomber said to have been a member of the "Islamic State." 

The Interior Ministry said the bomber entered the church, opened fire and then detonated an explosive vest.

However, there was conflicting information on how many suspects were involved in the attack. One security source, speaking on condition of anonymity, said two men were involved, including the one who blew himself up.

Church Bishop Moussa Khoury said an attacker also threw a grenade into the church during the afternoon Mass.

"He started shooting, went and then he blew up the church," he told The Associated Press.

A witness who identified himself as Rawad went on to tell AP that he saw the attacker accompanied by two others, who fled as the attacker was driving near the church.

First suicide bombing since toppling of Assad

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. 

The incident marks the first suicide bombing inside Damascus since Bashar al-Assad was toppled by an Islamist-led rebel insurgency in December. 

Syrian President Ahmed al-Sharaa, who led the offensive against Assad beforetaking over in January for a transitional phase, has repeatedly said he will protect minorities during his tenure.

Foreign ministers condemn violence

France condemned the attack and reiterated its commitment to "a transition in Syria that allows Syrians, whatever their religion, to live in peace and security in a free, united, pluralistic, prosperous, stable and sovereign Syria," Foreign Ministry spokesman Christophe Lemoine said.

The United Nations special envoy for Syria also voiced his outrage at Sunday's deadly attack, calling for a full investigation and action by the authorities.

A statement from the office of Geir Pedersen said he "condemns in the strongest possible terms the terrorist attack at St. Elias Church"," and "expresses his outrage at this heinous crime."