No group immediately claimed responsibility for the assault, but Syria’s Ministry of Interior Affairs reported to CNN that it was orchestrated by a “suicide bomber linked to the terrorist group ISIS.”

The attacker opened fire on the Mar Elias Church congregation in Damascus before “detonating an explosive vest,” the ministry explained in a statement.

A mass was being held at the church at the time of the attack, according to Syria’s state news agency SANA.

A video circulating on Syrian social media from inside the church shows dead bodies, significant destruction, shattered glass and broken chairs in the area where mass was being held, with blood visible throughout the scene.

It’s the first attack like it in Damascus since the Islamist-led rebel forces overthrew the Bashar al-Assad regime in December, ending a 13-year civil war which devastated the country, BBC reports.

Syria’s civil defence, popularly known as the White Helmets, said emergency teams were working to transfer the bodies to hospitals and secure the area.

“The treacherous hand of evil struck” on Sunday, the Greek Orthodox Patriarchate of Antioch said in a statement.

It wrote that “an explosion occurred at the entrance of the church, resulting in the deaths of numerous martyrs and causing injuries to many others who were inside the church or in its immediate vicinity.”

“We offer our prayers for the repose of the souls of the martyrs, for the healing of the wounded, and for the consolation of our grieving faithful.

“We reaffirm our unwavering commitment to our faith and, through that steadfastness, our rejection of all fear and intimidation,” the church said.

Greek Prime Minister Kyriakos Mitsotakis told the interim Syrian government it “must take concrete measures to protect all ethnic and religious minorities” within the country.

Syria’s interim President Ahmed al-Sharaa has promised he would protect all religions in the country since he took power; however, the nation has been hit by two waves of deadly and violent outbreaks since, not including yesterday’s bombing.

Ahmed al-Sharaa is a former al-Qaeda affiliate who was part of the Sunni Islamist group, Hayat Tahrir al-Sham (HTS). The group is recognised as a terrorist organisation by the UN, US and UK.

The United Nations Special Envoy for Syria, Geir O. Pedersen, expressed “outrage” at the “heinous crime,” his office said in a statement.

“Mr Pedersen calls on all to unite in rejecting terrorism, extremism, incitement and the targeting of any community in Syria,” the statement said.

“He sends his deepest condolences to the families of the victims and his hope for the recovery of those injured.”

The United States’ Special Envoy for Syria, Thomas Barrack, called the attack an act of “cowardice,” saying in a statement that it has “no place in the new tapestry of integrated tolerance and inclusion that Syrians are weaving.”

The foreign ministries of Turkey, Jordan, Iraq, Israel, Greece, Cyprus, the United Arab Emirates, Qatar, Saudi Arabia, the Palestinian Authority, Yemen, Oman, Bahrain, Ukraine, Austria, Belgium, the Czech Republic and the Netherlands also spoke out in condemnation of the attack.

The civil war in Syria has made it hard to report on the exact numbers of Greek Orthodox followers living in the country.

The community is the biggest of the Christian denominations in Syria, with an estimated number of followers believed to be in the several hundreds of thousands.