Two attackers armed with machetes filmed their deadly assault on a man in London, according to Sky sources.
The victim, reportedly a serving soldier , was hacked to death in broad daylight by the two assailants near an army barracks in Woolwich.
The two men were shot and wounded by police shortly after the killing, which was believed to be a politically-motivated Islamist terrorist attack.
Senior Whitehall sources said the two attackers, who are now in hospital, asked passers-by to film them, and they shouted "Allahu Akbar" (Allah is great).
In footage filmed by an onlooker, one of the attackers - wielding a bloodied meat cleaver and speaking with a London accent -says: "We must fight them as they fight us. An eye for an eye, a tooth for a tooth.
The black man, dressed in a grey hooded jacket and black woolly hat, apologises to members of the public who witnessed the horrific scenes before making a number of political statements.
"I apologise that women have had to witness this today, but in our land our women have to see the same. You people will never be safe.
"Remove your government, they don't care about you."
Footage and pictures show a frenzied scene at the junction of John Wilson Street and Artillery Place in Woolwich.
Some images show three men lying in the street, surrounded by discarded weapons and pools of blood.
One witness, identified as James Heneghan, said he and his partner saw two black men attack a young man aged around 20-years-old in a Help for Heroes T-shirt with kitchen knives like he was "a piece of meat".
"They were hacking at this poor guy, literally," he told LBC radio.
"They were hacking at him, chopping him, cutting him.
"They then stood around, waving knives and a gun, asking people nearby to take pictures of them "as if they wanted to be on TV or something".
He said they were running up and down the road, urging people to take pictures.
"In my opinion, they were waiting for the police to arrive to be shot by the police. That's the only thing I can think," Mr Heneghan said.
When armed police arrived 20 minutes later, "the man with the beanie hat, the tall guy, he charged at the police vehicle".
Another witness, Julia Wilders, 51, who lives near the scene, said she also saw one of the assailants run towards police clutching two meat cleavers.
"He ran towards police before they could even get out of the car, and it looked like the other one was going to lift the gun up," she said.
"We were driving back and my husband said to me 'don't look, they're resuscitating someone'. But apparently they were stabbing him."
Joe Tallant, 20, saw one man holding a gun and a knife, and another holding two knives.
He described how he saw the victim on the floor and the men asking onlookers to call the police.
"I looked on the floor and I saw a dead body and then I saw one of the men walking around the body," Mr Tallant said.
"He was telling people to call the police and then five to seven minutes later the police came.
"They walked towards the police car with their weapons and a police lady jumped out and shot them both."
He added: "They (the men) had the gun out and they were walking towards them casually with their arms by their side."I think there was a bit of twitching going on and then it all happened in a flash."