The US-led coalition against the Islamic State group said on Monday it killed a senior militant in Syria involved in the executions of an American aid worker and other Western hostages.
Abu al-Umarayn was involved in the November 2014 beheading of Peter Kassig, a former US Ranger who was doing volunteer humanitarian work when he was captured in 2013.
"He was killed and more information will be available after a full assessment," Sean Ryan, spokesman for the US-led coalition, said in a statement issued after the Sunday strikes.
"Al-Umarayn had given indications of posing an imminent threat to coalition forces and he was involved in the killing of American citizen and former US Army Ranger, Peter Kassig," he said.
Ryan said the militant had also been involved in the execution of several other prisoners.
It is the first time the coalition, which has been hunting down IS fighters in Iraq and Syria since 2014, has announced the killing of a militant leader linked to Kassig's death.
IS said they executed Kassig, a 26-year-old Iraq war veteran who was captured in Syria in 2013 and who reportedly converted to Islam while in custody, as a warning to the West.
He was captured in Syria, where he had been working to deliver supplies and provide first aid training to refugees.
"To Obama the dog of Rome, today we are slaughtering the soldiers of Bashar and tomorrow we are slaughtering your soldiers and with God's permission we will break this final and last crusade," a masked man said before he was shown beheading one of the soldiers.
Kassig's death was the fifth beheading of a Westerner carried out by the Islamic State.
Unlike in previous videos of Western hostages, Kassig did not appear alive in the video.