Evening Summary: A man has been killed, and two others injured, in an incident in Woolwich this afternoon, in what appears to be a terrorist attack. It's believed that the two injured people, who are now both in hospital, killed the victim with a meat cleaver. Read below for the latest updates, or follow the BBC's live coverage.
21.30 update: The attack has been condemned by political leaders from across the country, with David Cameron vowing that the country will "never buckle" in the fact of what is now being treated as a terrorist attack. The prime minister will also cut short his visit to France and return to Britain. The Ministry of Defence has also stepped up security at all military locations.
19.00 update: A video has emerged, apparently showing one of the attackers (warning: contains disturbing material). The man is covered in blood and speaks to the camera, at one point apparently saying "We swear by almighty Allah we will never stop fighting you" (although the line isn't audible in this clip).
17.30 update: A meeting of Cobra, the UK's emergency response committee, has been called by Home Secretary Theresa May to look into the attack. Earlier reports had suggested the Met weren't treating it as a terrorist incident.
17.00 update: LBC interviewed an eyewitness named James who tells a harrowing story of two men, in their mid-twenties, using meat cleavers to attack the victim, who was wearing a Help for Heroes T-shirt.
The police have also reported finding a number of weapons near the scene, including several knives and at least one firearm.
16.10 update: Speaking to BBC London, Local MP Nick Rainsford says that one person has been killed and two are seriously injured. He also said that the victim was a soldier serving in the Army. Here's the BBC's live coverage.
15.50 update: On Twitter, @BOYADEE claims to have witnessed the incident. His timeline has a pretty colourful description of what happened... thought we've no idea whether it is accurate.
According to various reports on Twitter there has been a fatal attack in Woolwich. Early suggestions are that one person has been decapitated, possibly in or around an army base, while armed police are also reportedly involved. There is some speculation that the victim was an army cadet. The air ambulance is also on the scene.
It's important to stress that nothing has been confirmed yet; the Metropolitan Police's Twitter has only this:
Officers respond to reports of an assault on John Wilson St, Greenwich. Updates to follow
— Metropolitan Police (@metpoliceuk) May 22, 2013
Here's a photo purportedly from the scene. More news as it develops.