Ese Awhotu with agency report
A video posted online claims to show that Islamic State militants have killed the captured US aid worker Abdul-Rahman Kassig.
The video shows a masked man standing over a severed head which he says is that of Mr Kassig.
The US says it is working to determine the authenticity of the video, which also shows a mass beheading of 18 Syrian troops.
Mr Kassig, also known as Peter, was captured last year.
According to BBC,his family, who live in the US state of Indiana, said they were awaiting confirmation of the reports about their “treasured son”.
“We prefer our son is written about and remembered for his important work and the love he shared with friends and family, not in the manner the hostage takers would use to manipulate Americans and further their cause,” the family said in a statement.
Kassig, a 26 year-old former U.S. Soldier had converted to Islam in captivity and also went by the name Abdul Rahman Kassig.
Following his return to civilian life, he became an aid worker in Syria, where he was captured and held hostage for over a year.
ISIS had threatened to kill Kassig in a previous video which showed the beheading of British aid worker, Alan Henning.
The US says it is working to determine the authenticity of the video, which also shows a mass killing of Syrian troops.