An air strike killed more than 40 members of the jihadist group Jabhat Fateh al-Sham in northwestern Syria on Thursday, January 19 night, the Syrian Observatory for Human Rights said, according to Reuters.

The group, formerly known as the Nusra Front, could not immediately be reached for comment.

The Observatory said the air strike had targeted a Fateh al-Sham base in a rebel-held area west of Aleppo, and it was not clear if it had been carried out by Russian or U.S. planes. The Nusra Front renamed itself Fateh al-Sham last year when it formally dissolved ties to al Qaeda.