A man has died and two are injured after police responded to a reported machete attack in south-east London.
The government is reported to be treating the attack as a suspected terrorist incident and the prime minister said it was "truly shocking".
Eyewitnesses said a man was assaulted in a Woolwich street by two individuals who were later shot by officers.
Local MP Nick Raynsford said the dead man was a soldier at Woolwich barracks but this has not been confirmed.
Home Secretary Theresa May has summoned a meeting of the government's emergency response committee to assess the incident.
It is understood she has also requested updates from the Metropolitan Police Commissioner, Bernard Hogan-Howe, and the head of MI5.
BBC political editor Nick Robinson said the police view is that the the attack may have been filmed and footage may exist.
People carrying out the attack were of Muslim appearance and cries of God is Great or Allahu Akbar were heard, said our political editor.
London Ambulance Service confirmed one man had been found dead at the scene.
It said two men had been taken to hospital, one in a serious condition.
One of the men was airlifted from the scene, and another was taken away by road ambulance
A spokesperson said an air ambulance and four crews had attended the scene.
Witnesses reported by the Press Association said two people had been shot after armed police were called to an incident in which a man was attacked with a machete-style knife.
One witness, identified only as James, said two men had attacked another man, aged about 20, who was wearing a T-shirt of military charity Help for Heroes.
"These two guys were crazed. They were just animals. They dragged him from the pavement and dumped his body in the middle of the road and left his body there," he told LBC radio.
He said after the "horrendous" attack, the two men, who were also in their 20s, stood around, waving knives and a gun, and asked people to take pictures of them "as if they wanted to be on TV or something".
"They were oblivious to anything, they were more worried about having their photo taken, running up and down the road," he said.
Thomas, a witness who contacted the BBC, said: "I got there minutes after it happened because you could hear gunshots from Woolwich High Street.
"Basically two men carried out an axe attack on a young army cadet walking along the street, by the looks of things the police responded and then shot them in front of the public, at the same time I couldn't really tell if the cadet was fatally or not hurt as police were crowded around him."
UPDATED the story*
Source: http://www.bbc.co.uk/news/uk-22630303
Mirror having some live updates: http://www.mirror.co.uk/news/uk-news/woolwich-major-incident-live-updates-1904508
Some 'Eyewitness' reports:
Julia Wilders, 51, of Charles Grinling Walk, told the News Shopper: "I saw some blokes trying to resuscitate another man on the floor.
"We walked down to have a look and we saw a black bloke walking up there with a gun.
"Another bloke had two meat cleavers in his hand.
"A response team turned up.
"One of the blokes ran to the police car with the meat cleaver and they shot him.
"And then they shot the other one."
London Air Ambulance have confirmed that one patient was airlifted from the scene, while another was taken away by road ambulance. They are conflicting reports as to whether they have died from their injuries.
An eyewitness called James told LBC that the attackers treated their victim as a "piece of meat'' after he was dead.
He said: "These two guys were crazed. They were just animals. They dragged him from the pavement and dumped his body in the middle of the road and left his body there.
The victim was apparently wearing a Help for Heroes t-shirt and was attacked with a machete-style knife and dumped in the street.
One witness, identified as James, said he and his partner saw two black men attack the young victim with knives, including a meat cleaver.
"They were hacking at this poor guy, literally," he told LBC.
"They were hacking at him, chopping him, cutting him."
Twitter user Boya Dee has claimed he witnessed the horrific attack.
He wrote: "Ohhhhh myyyy God!!!! I just see a man with his head chopped off right in front of my eyes!
"Mate ive seen alot of s*** im my time but that has to rank somewhere in the top 3. I couldn't believe my eyes. That was some movie s***.'
"The two black men run this white guy over then hop out the car and start chopping mans head off with machete!!
"People were asking whyyy whyyy they were just saying we've had enough! They looked like they were on something! Then they start waving a revolver
"Then thats how you know they were on something cause they actually went for armed feds with just two machete and an old rusty looking revolver.
'"The first guy goes for the female fed with the machete...Then the next man tries to fire off the rusty 45 and it just backfires and blows mans finger clean off..."
Supposed video of the suspect. Can be NSFW/NSFL.
http://vimeo.com/66751726