Syrians call for ISIS to release U.S. aid worker

TRIPOLI, Lebanon -- Several Syrian friends of an American aid worker held by the Islamic State of Iraq and Syria (ISIS) and threatened with beheading have called for his release, saying he converted to Islam and was helping Syrians.

The friends of Peter Kassig, who became Muslim while in captivity and changed his name to Abdul-Rahman Kassig, held a news conference in Tripoli, Lebanon, a city that witnessed clashes last month between Muslim militants and Lebanese troops.

The 26-year-old Kassig was captured in October 2013. The Indianapolis native is a former Army Ranger who was honorably discharged after serving in the Iraq War, according to his parents.

Kassig went to the Middle East in 2012, first as a medical worker in Lebanon, helping Palestinian and Syrian refugees. Later that year, Kassig started a non-governmental organization called Special Emergency Response and Assistance (SERA) to respond to the needs of Syrians attempting to escape their country's civil war.

"We are demanding the Islamic State to release him, if they know Islam," one of Kassig's friends, Amjad al-Moghrabi, told reporters Saturday. "He is a Muslim and has not participated in what his country is doing." al-Moghrabi was referring to airstrikes by the U.S.-led coalition against ISIS in Iraq and Syria.

"Our demand is to release him and to return (him) to his family because as a person he helped us and we should ask for mercy for him," said Dr. Ahmad Obeid. "He is unfortunately detained so we are calling for his freedom because he supported our cause, and we cannot leave him and let them hurt him."

In the room where the news conference was held, some of Kassig's friends held banners that read in Arabic and English: "Justice for Abdul-Rahman."

So far, ISIS has beheaded four Western captives: American reporter James Foley; American-Israeli journalist Steven Sotloff; aid worker and former U.K. air force engineer David Haines; and Alan Henning, a taxi driver from northwest England, an aid worker in Syria.

In a video showing Henning's execution in October, a man believed to be Kassig is shown kneeling as a masked ISIS militant threatens that Kassig will be the next hostage to be beheaded if airstrikes continue.

Kassig's parents have pleaded with ISIS to release him. In an interview with CBS News last month, Ed and Paula Kassig revealed that they had received a horrifying audio recording of their son two weeks prior -- the first time they had heard his voice in over a year.

"I have to try," Paula Kassig said of the family's direct appeals to the militants. "Because I need to know that I've done everything I can do."

Ed Kassig said his son's captors have not asked for anything the couple can provide.

"They demand. They simply demand," he said.

"Their demands have always been ones that we cannot accommodate," Paula added. "We have sent them back messages that we cannot do what you ask. We have tried. But we don't have the power to do it."

In addition to Kassig, ISIS also holds British photojournalist John Cantlie, who has appeared in six propaganda videos released by the extremist group.