This man was photographed brandishing a knife and speaking to a woman at the scene
A man killed in a suspected terrorist attack in south-east London was a member of the armed forces, senior Whitehall sources have confirmed.
Two men spent the night under arrest in hospital as counter-terrorism police investigate the killing in Woolwich.
One man - his hands covered in blood- was filmed by a passer-by, saying he carried out the attack because British soldiers killed Muslims every day.
The PM is to chair a Cobra emergency response committee later.
David Cameron flew back from France yesterday to lead the government response. The meeting will be attended by politicians, the UK's most senior police officer and the new head of MI5.
Meanwhile, security has been increased at barracks across London.
The two suspects were shot and wounded by police after the attack - which took place in John Wilson Street, the A205, at 14:20 BST.
One is in a serious condition while the other is also being treated for injuries.
Eyewitnesses say the victim was hacked to death by two men shouting Islamist slogans.
The men made no attempt to flee and encouraged people to take pictures of them and their victim.
One of the men was filmed wielding a bloodied meat cleaver and making political statements.
"I apologise that women have had to witness this today, but in our land our women have to see the same," he said.
"You people will never be safe. Remove your government, they don't care about you."
The other was pictured holding a knife and speaking to a woman at the scene.
According to the paper, Cub Scout leader Ingrid Loyau-Kennett asked him: "Would you like to give me what you have in your hands?"
"He was covered with blood," she said. "I thought I had better talk to him before he starts attacking somebody else."
She says the suspect told her the dead man was a British soldier, adding: "I killed him because he kills Muslims over there and I am fed up that people kill Muslims in Iraq and Afghanistan."
A vehicle believed to be involved in the incident has been towed away from the scene - it is thought the victim may have been hit by the car before he was attacked.
The Muslim Council of Britain said the murder was "a truly barbaric act that has no basis in Islam and we condemn this unreservedly".
Meanwhile, a man was arrested on suspicion of attempted arson and possession of an offensive weapon at a mosque in Braintree, Essex, on Wednesday night.
At a press conference with French President Francois Hollande in Paris, Mr Cameron said Britain would "never buckle" in the face of terror attacks.
"People across Britain, people in every community, I believe, will utterly condemn this attack," said Mr Cameron, who was previously planning to stay in Paris on Wednesday night.
Met Police Commissioner Bernard Hogan-Howe, MI5 director general Andrew Parker, Home Secretary Theresa May, Defence Secretary Philip Hammond and Mayor of London Boris Johnson are among those expected to attend Thursday morning's Cobra meeting.
Meanwhile, armed forces personnel based in London and elsewhere have been told to be more vigilant.
That is on top of the extra precautions now being taken at London's 10 or so main barracks.
BBC defence correspondent Caroline Wyatt said that, since British forces intervened in Iraq and Afghanistan, they and their families have been well aware they might be targets at home.
At least two plots by Islamic extremists to kill soldiers in the UK have been foiled in recent years.