A video apparently showing the beheading of British hostage Alan Henning, who was kidnapped by IS militants, has been released on the internet.
The video appears to show Mr Henning say: "I am Alan Henning. Because of our Parliament's decision to attack the Islamic State, I, as a member of the British public, will now pay the price for that decision."
The man dressed in black, who speaks with a British accent, then makes a direct statement to Prime Minister David Cameron: "The blood of David Haines was on your hands Cameron. Alan Henning will also be slaughtered, but his blood is on the hands of the British Parliament."
The video then apparently shows the militant alongside former American soldier Peter Kassig.
The militant says: "Obama, you have started your aerial bombardment in Sham [Syria], which keeps on striking our people. So it is only right that we continue to strike the necks of your people."
Mr Henning, a former taxi driver from Salford, was last seen at the end of a video released last month following the beheading of fellow British captive David Haines.
Prime Minister David Cameron said the "brutal murder" of aid worker Alan Henning by Islamic State "shows just how barbaric and repulsive these terrorists are", and vowed to "do all we can to hunt down these murderers and bring them to justice".
Earlier this week Mr Henning's wife Barbara pleaded for him to be freed.
She said: "I ask Islamic State please release him, we need him back home."
She added: "Some say wrong time, wrong place. Alan was volunteering with his Muslim friends to help the people of Syria. He was in the right place doing the right thing."
Mrs Henning revealed she had received an audio message of her husband pleading for his life, and had been told that a Sharia court had found him innocent of being a spy.
She told BBC News: "We are at a loss why those leading Islamic State cannot open their hearts and minds to the truth about Alan's humanitarian motives for going to Syria and why they continue to ignore the verdicts of their own justice system.
"Surely those who wish to be seen as a state will act in a statesmanlike way by showing mercy and providing clemency. I ask again, supported by the voices across the world, for Islamic State to spare Alan's life."
The Foreign Office said: "We are aware of the video and are working urgently to verify the contents. If true, this is a further disgusting murder.
"We are offering the family every support possible; they ask to be left alone at this time."
MPs were swift to condemn the apparent murder, one describing it as "an attack on humanity".
Liberal Democrat party president Tim Farron said: "Alan Henning should be remembered for what he was - a kind hearted, selfless man who wanted to help others. My prayers are with his family."
Shadow cabinet minister Jonathan Ashworth said the video emerged only hours after a vigil for his safe return by people "of all faiths and none" in Leicester.
"Dreadful devastating news," he said.
Labour's Pat McFadden said it was the "senseless killing of an innocent man. An attack on humanity."
More to follow...