WARNING - STORY CONTAINS GRAPHIC IMAGES
Amateur video obtained by ITV news shows a man with bloodied hands and a knife just after a man was killed near an army barracks in London.
Media reports say the dead man was a British soldier who was hacked to death by unidentified assailants. Some reports suggested his attackers tried to behead him while shouting "God is greatest" in Arabic.
British Prime Minister David Cameron called an emergency security meeting after the man was killed.
Britain's government convenes meetings of its emergency security committee only to deal with incidents that have implications for national security.
London's mayor said it was overwhelmingly likely the killing was a terrorist attack.
Security was tightened in the area immediately after the attack but details are sketchy.
