U.S. officials say a key leader of Islamic State in its de facto capital of Raqqa, Syria was killed by a coalition airstrike this week, confirming earlier reports.

A statement by the U.S.-led coalition Thursday said Abu Jandal al-Kuwaiti was killed in a strike near near Tabqa Dam on Monday. It said he was a previous member of IS's War Committee.

“Abu Jandal was involved in the use of suicide vehicles, IEDs and chemical weapons against the SDF. Because of his associations with ISIL terror attack planners and War Council members, his death will degrade ISIL's ability to defend Raqqa and launch external operations against the West,” the statement said.

The coalition said he also participated in the retaking of Palmyra before sent to Tabqa with the mission to improve Islamic State defenses against the U.S. backed Syrian Democratic Forces (SDF).

Britain-based Syrian Observatory for Human Rights, which monitors the war, reported Tuesday that al-Kuwaiti was a target by U.S. led coalition aircraft and IS supporters shared on social media that he was dead.

The SDF, a coalition of Kurdish and Arab forces, launched its Raqqa offensive in early November, routing Islamic State fighters from the northern part of the province.

The ongoing offensive consists of two major front lines where SDF units, with the help of U.S. air support, are approaching Raqqa from the west, attempting to encircle the city and cut a highway link between Raqqa and the eastern city of Deir Ezzor, another IS stronghold.

The U.S. recently announced it has assigned another 200 troops to Syria to train and advise local fighters battling IS, joining 300 American fighters already authorized to operate in Syria.