British Prime Minister David Cameron has condemned the group which calls itself the Islamic State for killing a British aid worker David Haines, the third such killing in recent weeks.
Cameron said: "The fact that an aid worker was taken, held and brutally murdered at the hands of ISIL, sums up what this organisation stands for. They boast of their brutality, they claim to do this in the name of Islam. That is nonsense, Islam is a religion of peace. They are not Muslims, they are monsters."
The 44-year-old father-of-two was working for a French aid agency when he was kidnapped in Syria in March 2013.
He was killed in the same manner as US journalists James Foley and Steven Sotloff, who were also abducted in Syria, and by the same abductor: a masked man with a British accent.
In the latest video, titled "A Message to the Allies of America", he addresses Cameron:
"Your evil alliance with America which continues to strike the Muslims of Iraq ... will only accelerate your destruction ... playing the role of the obedient lapdog, Cameron, will only drag you and your people into another bloody and unwinnable war."
The sort of videos that the Islamic State group has released - aimed at a western audience and showing the death of a western hostage - haven't been seen in nearly a decade.
So why is IS turning back the clock? And are hostages being used as a new weapon of war?
Presenter: Nick Clark
James Alvarez - a hostage negotiator and psychologist.
Donatella Rovera - senior crisis response adviser at Amnesty International.
Bilal Abdul Kareem - a freelance journalist and writer, and specialist on armed groups in Syria.
Live Box 201493123623889276
Source: Al Jazeera