The video shows a militant dressed in black holding up what he claims to be the severed head of Kassig.
The militant in the video has reportedly been rumoured as Jihadi John, a British born jihadist, despite previous reports that he had been injured in an air strike.
UK AID WORKER MURDERED IN SYRIA
Kassig was captured last year whilst helping proved medical aid in Syria. His family revealed that he converted to Islam whilst in captivity on his own free will.
Just last month Kassig’s parents released lines from a letter that he wrote to them after he had been taken hostage.
They read: "This is the hardest thing a man can go through, the stress and fear are incredible," the aid worker wrote.
"They tell us you have abandoned us and/or don't care but of course we know you are doing everything you can and more.
TEENS WHO RAN AWAY TO FIGHT IN SYRIA ARE 'PREGNANT' AND WANT TO COME HOME
"Don't worry Dad, if I do go down, I won't go thinking anything but what I know to be true. That you and mom love me more than the moon and the stars."
The government is currently in talks with Internet providers to try and prevent beheading videos- such as those filmed byIslamic State- from appearing online.
Our thoughts go out to Kassig’s family during this difficult time.