Islamic State militants fighting in Iraq and Syria claim they have beheaded American hostage Peter Kassig, also known as Abdul Rahman Kassig.

A video posted online on Sunday did not show the purported execution of the aid worker, but did show a masked man with a decapitated head covered in blood lying at his feet.

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Speaking English in a British accent, the man says: “This is Peter Edward Kassig, a US citizen.”

Reuters said it could not immediately verify the authenticity of the footage, which appeared on a jihadist website and on Twitter feeds used by ISIL.

The video also purportedly showed a number of other people being beheaded.

In October Mr Kassig appeared in a video that militants released after the death of British aid worker Alan Henning.

Soon afterwards Mr Kassig’s parents, Ed and Paula from Indianapolis, Indiana, released a statement confirming their 26-year-old son had been taken captive while doing humanitarian work in Syria.

Mr Kassig served in the US Army during the Iraq war before being medically discharged, his family said.

Pentagon records show he spent a year in the army as a ranger and was deployed to Iraq from April to July 2007.

After leaving the army, Mr Kassig became an emergency medical technician and travelled to Lebanon in May 2012, volunteering in hospitals and treating Palestinian refugees and those fleeing Syria’s nearly four-year civil war, his family said in October.

He was detained on October 1, 2013, while travelling to the eastern Syrian city of Deir al-Zor while working for Special Emergency Response and Assistance, a non-governmental organisation he founded in late 2012 and based in southern Turkey to treat refugees flowing across the border from Syria, his family said.

While in captivity, he converted to Islam and took the name Abdul Rahman.