WASHINGTON (Reuters) – A red-bearded Islamic State commander described by American officials as the group’s de facto minister of war may have been killed in an air strike in Syria on Friday by the U.S.-led coalition, several U.S. officials said on Tuesday.

Abu Omar al-Shishani, also known as Omar the Chechen, ranked among the most wanted militants under a U.S. reward program that offered up to $5 million for information to help remove him from the battlefield.

Born in 1986 in Georgia, which was then still part of the Soviet Union, Shishani had a reputation as a close military adviser to Islamic State’s leader Abu Bakr al-Baghdadi, who was said by followers to have relied heavily on Shishani.

He may have been killed during a coalition strike on March 4 near the town of al-Shadadi, which U.S.-backed forces from the Syrian Arab Coalition captured from the Islamic State last month.

Two U.S. officials expressed optimism about the strike but acknowledged that a determination about Shishani’s fate was not certain and that the results of the operation still were being reviewed. A third official limited himself to saying Shishani was targeted in the strike.

The U.S. State Department described Shishani as a senior Islamic State commander and Shura Council member based in al-Raqqa, the Islamic State’s de facto capital in Syria.

It said he was identified as the Islamic State’s military commander in a video distributed by the group in 2014.

Shishani, whose name was originally Tarkhan Tayumurazovich Batirashvili, oversaw a prison facility near Raqqa where Islamic State possibly held foreign hostages.

(Additional reporting by Jonathan Landay; Editing by Bill Trott)