BEIRUT (AP) — The U.S.-led coalition has targeted a senior member of the Islamic State group involved in the 2014 killing of American aid worker Peter Kassig, a military spokesman said Monday.

Col. Sean Ryan, a spokesman for the U.S.-led coalition fighting IS, told The Associated Press that coalition forces conducted precision strikes against Abu al-Umarayn and several other IS members. He said the strikes, which took place on Sunday, occurred in a desert area in southeastern Syria.

The area is close to where Syria's state news agency said the U.S.-led coalition fired several missiles at Syrian army positions in the country's east, causing material damage. The SANA report said positions targeted on Sunday night are in the Ghorab Mountains, south of the eastern town of Sukhna.

The Britain-based Syrian Observatory for Human Rights, a war monitoring group, said U.S. troops in the Tanf base near the Jordanian and Iraqi border fired 15 rockets at a Syrian military convoy that lost its way in the area. It gave no further details.

However, Mozahem al-Salloum, from the activist-run Hammurabi Justice News network that tracks developments in eastern Syria, denied reports that U.S. troops targeted Syrian army positions. The targets were only IS elements, al-Salloum added.

Attacks by the U.S.-led coalition against Syrian troops have been rare. In 2016, warplanes of the U.S.-led coalition bombed Syrian army positions in the eastern city of Deir el-Zour and killed dozens of soldiers.

Ryan, the military spokesman, said Abu al-Umarayn had given indications of "posing an imminent threat" to coalition forces and that he was involved in Kassig's beheading. He also said Abu al-Umarayn was linked to and directly involved in the killings of several other prisoners of IS.

Kassig was captured Oct. 1, 2013, while delivering aid in Syria through a relief organization he founded. He converted to Islam during captivity and changed his first name to Abdul-Rahman.

His parents, Ed and Paula Kassig, had issued numerous appeals for his release after his life was threatened in an October 2014 IS video that showed the beheading of a fellow aid worker, Britain's Alan Henning.

In mid-November 2014, IS released a video showing that Kassig, 26, was beheaded. The White House confirmed Kassig's death two days later.

Over the past years, the U.S.-led coalition has killed top IS officials in Syria and Iraq.