An Islamic State group leader involved in the execution of American aid worker Peter Kassig and other Western prisoners was targeted in a strike Sunday by the US-led anti-jihadist coalition in Syria.
Kassig, aged 26 at the time of his death, was among a group of prisoners decapitated by jihadists in November 2014. The mass execution was shown in a video released by the group.
"Coalition forces conducted precision strikes against a senior ISIS member, Abu al Umarayn, and several other ISIS members in the Badiyah Desert, Syria," said Sean Ryan, spokesman for the US-led coalition, in a statement in English.
"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 U.S. Army Ranger, Peter Kassig", kidnapped in Syria in 2013, he added.
Ryan said he had been also been involved in the execution of several other prisoners.
"Coalition airstrikes continue to disrupt ISIS command and control on the battlefield as we remove key figures from their ranks," he said.
Damascus had earlier Sunday accused the coalition of launching missiles against Syrian army positions, according to the official Sana news agency.
"The American coalition forces launched around 8:00 pm (1800 GMT) this evening several missiles against some positions of our forces in the Ghorab mountains south of Sukhna," causing only "damage to equipment," Sana said, citing a military source.
According to the monitoring Syrian Observatory for Human Rights, coalition forces positioned in the Al-Tanf region fired "more than 14 missiles" at a Syrian army convoy as it was passing through the desert in the far east of Homs province.
"The group was lost in the middle of the desert around 35 kilometres from the Al-Tanf base" of US and British troops, the Observatory's director Rami Abdel Rahmane told AFP.
The United States generally uses this base to launch its strikes against IS jihadists. It has also been used in the past to train Syrian opposition fighters.
Peter Kassig founded a humanitarian organisation in 2012 that trained some 150 civilians to provide medical aid to people in Syria. His group also gave food, cooking supplies, clothing and medicine to the needy.
He took the name Abdul-Rahman after converting to Islam.
Before Kassig's death, his life had been threatened in an earlier video showing the beheading of another aid worker, Briton Alan Henning.
Kassig's mother Paula reached out directly to IS militants to plead for her son's life.
The international coalition intervened in Syria and Iraq in 2014 to fight the expansion of IS after it had taken control of vast swathes of territory straddling the two countries.
Defeated in Iraq, the group still retains territory in some parts of the Syrian desert, particularly in the east of the country, where the coalition continues to fight the jihadists with the support of an alliance of Kurdish and Arab fighters.