An explosion on a bus carrying Iranian pilgrims in Damascus killed at least six people and injured dozens more, the BBC reported this morning. The bus had apparently stopped to refuel at a petrol station about 500 meters from a Shia Muslim shrine when it exploded.

Al-Jazeera reports that the blast occurred as the driver of the bus and his assistant were making repairs at the back of the bus; other reports suggest that the blast could have been caused by a gas canister carried by one of the pilgrims in their luggage. Also according to Al-Jazeera, the explosion took place as Saeed Jalilee, an important Iranian security official, was visiting Damascus.

Incidents such as this are rare, the BBC reports, but one similar explosion happened in September 2008, killing 17 people on a road leading to the same shrine. The attack then was blamed on Fatah al-Islam, a Sunni group; there is no word whether this explosion can be linked to any group.