The death of a U.S. aid worker at the hands of Islamic State of Iraq and Syria (ISIS) militants is "barbaric" and is not a true reflection of Islam, a cleric told hundreds of people who gathered Friday for the first of three memorial services honoring the slain man.

Sikh Muhammad al-Yaqoubi, a top Syrian cleric who has been a strident critic of ISIS, called Peter Kassig, 26, a "great hero" during prayers at the Al Huda Foundation mosque in Fishers, a suburb of the Midwestern city of Indianapolis. He said Kassig "carried in his heart the principles of Islam even before becoming Muslim."

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 ISIS video that showed the beheading of a fellow aid worker, Britain's Alan Henning.

The Muslim community in Indianapolis rallied around the Kassigs, participating in prayer vigils and rallies urging his captors to follow the Quran's teachings that prohibit Muslims from killing other Muslims.

Their support continued Friday, five days after the White House confirmed Kassig's death.

"What happened to Abdul-Rahman is beyond comprehension. It is barbaric. But it is not Islamic. It is against Islam," al-Yaqoubi told those gathered Friday.

Kassig's parents did not speak to the media at the service but issued a statement that was released afterward.

"We are thankful that Abdul-Rahman had his faith to sustain him and carry him through his ordeal," they said.
Services also are planned Saturday at a gathering of the Muslim Alliance of Indiana and Sunday at Butler University in Indianapolis.

Asked after the service if anything could have been done differently to save Kassig, al-Yaqoubi said it would have been hard to save him from ISIS.

"Terrorists are terrorists, wherever they exist, ISIS has shown no signs of negotiation, they have shown every type of challenge to the people of the international community," he said.

But Shaker Rashid, imam of the Al Huda Foundation, said the tragedy could have been prevented if international leaders had stepped in to remove Syrian President Bashar Assad from power. ISIS extremists initially fought to oust Assad.

AP