Four members of the oil facilities security forces were killed on Thursday in Deir ez-Zor, eastern Syria, after their bus was targeted by an explosive device, according to Syrian sources.

The Syrian Arab News Agency (SANA) reported that “four workers from the oil facilities guard in Deir ez-Zor were killed and nine others — including workers and civilians — were injured today as a result of a terrorist attack using an explosive device that targeted an employee transport bus belonging to the Ministry of Energy.”

The agency quoted a statement from the Ministry of Energy saying that the bus was hit by an explosive device “while it was traveling on the road between the cities of Deir ez-Zor and Al-Mayadeen.”

Meanwhile, Agence France-Presse (AFP) cited an official source saying that “five personnel from the Syrian Ministry of Defense were killed when their bus was targeted.”

The source added that “a directed explosive device detonated as a bus carrying oil facilities guards affiliated with the Ministry of Defense was passing by, killing five of them and injuring 13 others, including civilians who happened to be on the road.”

According to Syrian state television, an explosive device targeted an “employee transport bus” on the Deir ez-Zor–Al-Mayadeen road in Deir ez-Zor province.