A man was seen running with a machete after "wrenching it" from a pair of motorcyclists who then chased him with a hammer outside a Tube station.
Commuters watched in horror as the two thugs reportedly attacked the man outside Elephant and Castle Underground station at around 6.20pm on Saturday.
"I could see the long blade. I just thought I was going to see someone die," one woman told the Mail Online.
The incident, thought to be a suspected robbery, was caught on video by witnesses.
One clip shows a man in a motorcycle helmet and a purple printed jacket running across the road with a machete in his hand.
A motorbike is seen lying on its side in front of a car, reports My London.
Witnesses said he had wrestled the knife off of two men on a moped who were attacking him.
The man sprints onto the pavement and quickly moves out of the way as two people approach him on a moped.
Then the pair swerve and turn around in the middle of the road, when the passenger can be seen holding a hammer.
One woman, who was visiting from Gloucestershire, described it as "one of the worst things I have ever seen."
The 30-year-old said: "I was walking back to Elephant and Castle and something didn't feel right. There was a bike on the floor, and another facing the wrong way.
"I was walking with my aunt and I said 'that man's got a knife'."
The victim managed to avoid the two men by standing on the pavement and then running before they fled, the video suggests.
One brave man got out of his car to help the man who was being attacked, according to witnesses.
Another clip shows him removing a weapon from the scene.
Police rushed to the Tube station but those involved had already fled on mopeds.
The Met said a machete was recovered from the scene. There were no reports of any injuries and enquiries are ongoing.
Anyone with information on what happened is asked to call the Met Police on 101 quoting reference 5535/23APR.
