Shocking footage shows an attacker wielding a sword in the latest moped crime on the streets of London.
The video shows the aftermath of an incident in Barking in the east of the capital last weekend when two armed attackers set upon an 18-year-old.
It shows one of the pair, apparently clutching a samurai-style sword, falling off the back of the bike as they attempt to make off.
The footage, published on YouTube, shows pedestrians shouting at the pair as they disappear into the night.
The victim attempted to hide in a local supermarket as he fled from the pair, the Barking and Dagenham Post reported.
But he was attacked in the shop and taken to hospital with head injuries. Doctors have since said his wounds are not life-threatening.
Police are appealing to anyone who saw the attack or has any information to come forward.
A Scotland Yard spokesman said: 'Officers were called at approximately 22:10hrs on Saturday, 13 May after the incident in a shop in Ripple Road.
'The victim, an 18-year-old man, was walking along when he became aware he was being pursued by two males. He began to run and the suspects pursued him.'
The spokesman added: 'Fearing for his safety, the victim ran in to a shop to seek refuge but the suspects followed him - both were armed with knives. The suspects attacked the victim inside the shop, leaving with a head injury before they fled the scene on a moped.'
'The victim attended hospital for treatment to his injury - this is not life threatening.'
It is the latest moped-related crime in London, which has seen a spate of thefts and robberies carried out by gangs on motorised scooters.
More than 11,389 motorbike incidents, including thefts, robberies and acid attacks, took place in London alone last year.
The Daily Mail reported last week how the gangs are throwing off their helmets to escape being chased by police, who follow an 'unwritten' health and safety rule that means their career is at risk if they endanger the thugs by pursuing them.
Anyone with information on the latest incident is asked to call Trident officers on 020 8217 7378 or contact Crimestoppers, anonymously, on 0800 555 111.