Various online reports have confirmed what is being reported as a "major incident" in Woolwich in South East London, as people drop feed information about what the Metropolitan Police has so far described as an "assault".
Eyewitnesses have reported a beheading with a 'machete' or 'meat cleaver' and claimed that police armed units responded to a scene in John Wilson Street, Woolwich.
The shots are said to have been fired close to the Royal Artillery Barracks in London after an alleged sword attack, The Sun reports.
While the incident has yet to be confirmed, local residents and social media users report that two black men ran over a white man in a car, before "hopping out" and attempting to decapitate him. It is not yet known if the attempt was successful, though reports suggest that the two men were shot by armed police arriving at the scene.
The Boyadee Twitter account has what claims to be an eyewitness report of the incident, though its veracity is yet to be confirmed.
One man working in nearby Woolwich New Road told the News Shopper website: "All I heard was a couple of people had been shot. "It was about an hour or so ago. I heard they were trying to behead someone and were shot by police."
Police were called to the scene in South east London, at around 2.20pm today and the immediate area was shut down.
A Scotland Yard spokesman said: "Officers have responded to an incident in John Wilson Street at 2.20pm today.
Reports also suggest that the victim was a serving soldier.
UPDATE: An eyewitness told LBC Radio that, "five feet away there was a blue Vauxhall if I'm not mistaken" that has "crashed into a signpost".
There were, he said, "two guys with what we know know is the victim, who was on the floor. We thought they were helping him."
He then said his partner let out an "almighty scream" and saw "big knives like that from a butchers". He stated there was "no samurai sword" but the attackers were "hacking at the poor guy [on the floor]" with a "meat cleaver".
One of the men is then reported to have pulled a gun from the car and told witnesses to get back in their cars. The eyewitness then told LBC Radio that the men were "chopping this guy to pieces, literally hacking at something like it was a piece of meat. These guys were animals. They then dragged the poor guy, he was obviously dead.... dragged him from the pavement an dumped his body in the middle of the road".
The men are then reported to have stood at the side of the road, waving a gun and knives about. Armed response units apparently took 20 minutes to arrive on the scene, and police "at the end of the road" did not respod to the event, according to the eyewitness, because they were not armed and able to deal with the incident. The eyewitness said there were "brave women" with the man on the floor who were trying to shield the body. "There were people filming it on their phones". One of the attackers then approached a bus and told people to take photos of him, after the incident.
"There were six shots fired and both men went down... I'd say they were in their mid-20s".
Note: the eyewitness information was transcribed live from LBC Radio. We apologise in advance for any errors.