A major police operation has been launched after two suspected terrorists murdered a man in the street in broad daylight.
Eyewitnesses said the victim was hacked to death, with some suggesting his attackers tried to behead him, before charging at police when they arrived on the scene in Woolwich, south east London.
A local MP said the victim was believed to be a soldier.
British Prime Minister David Cameron said that there were "strong indications" that a killing in London was terror-related.
"It is the most appalling crime," Cameron said, before cutting short a visit to Paris.
"The police are urgently seeking the full facts about this case but there are strong indications that it is a terrorist incident."
The Independent Police Complaints Commission (IPCC) has started an investigation in to the circumstances surrounding the shooting of the two suspects. This is a matter of routine when officers use their firearms.
A commissioner has been appointed to lead the investigation and twelve IPCC investigators are currently at the scene and viewing CCTV footage.