According to monitor the Syrian Observatory for Human Rights, an airstrike against ISIS forces in the Hasakeh Province has killed a pair of ISIS leaders, Abu Osama al-Iraqi and Amer al-Rafdan. They said it was unclear if it was a US or Syrian airstrike.
Abu Osama al-Iraqi is an Iraqi militant who previously had ties to the Kalimat al-Haq organization. It is unclear what his position within ISIS was, but he was alleged to have had a role in the strikes around Baghdad during the most recent election.
Amer al-Rafdan was identified at one point as the ISIS Emir of Deir Ezzor Province, though he had also been reported slain last year by al-Qaeda’s Nusra Front in fighting in that province. He had defected from Nusra to ISIS during the leadership dispute between the two.
ISIS has been moving into the Hasakeh Province in force in recent weeks, fighting Kurdish forces and Syrian military over the capital of Hasakeh. With Syrian military and Kurdish YPG assets on the ground in the area, either a Syrian airstrike or a US airstrike in support of the Kurds is possible, and neither has claimed credit for it.