Seven Iranian-backed militia fighters were killed in suspected U.S. strikes on Iranian targets in eastern Syria before daybreak Tuesday, a war monitor reported.

A series of explosions rattled Syria's eastern province of Deir al-Zour, coinciding with the presence of unidentified drones flying overhead.

The blasts were accompanied by intensified air strikes targeting military installations belonging to the Syrian army and Iranian-backed militias in several cities, including al-Bukamal, al-Mayadeen, and the eponymous provincial capital of Deir al-Zour, according to the Syrian Observatory for Human Rights.

The Britain-based watchdog group said it could not confirm the party responsible for the air strikes, saying they were possibly conducted by the U.S. military with possible involvement of Israel.

The observatory said a commander was killed in the attack without identifying him.

The Syrian government and Iranian authorities have not immediately commented on the reported air strikes or the drone presence, but opposition activists suggested the air strikes were carried out by U.S. forces.