Four people were killed and several injured on Thursday in an explosion in the mostly Christian Bab Sharqi district of Damascus’ Old City, near the Greek Orthodox Virgin Mary Church. Syrian state-run TV said it was a suicide bomb; opposition forces said it was a government-fired mortar.

No one had claimed responsibility, and it was unclear if the church was the intended target. The Associated Press said it was the first reported suicide attack inside the Old City, and that the bomb went off 50 metres from the church entrance.

“A terrorist bombed himself nearby the Patriarchate, next door to the Shi’ite association. Four persons were killed and 11 injured, one of them a woman working at the Patriarchate,” according to Open Doors International. But the victims most likely were Shi’ites, the organization said, because the bombing occurred at a Shia medical center next to the church.