Police officers from Scotland Yard's Flying Squad staged a dramatic raid on a hammer-wielding gang which was poised to rob a jewellery shop.
Following a series of robberies by an eastern European gang on jewellers in north-east London, Flying Squad officers launched an investigation codenamed Operation Tiburon.
Officers monitored the gang and leapt into action as the men approached a shop in Turnpike Lane, Haringey, and attempted to carry out the robbery.
A Metropolitan Police spokesman said a struggle ensued and one of the gang tried to attack an officer with a hammer.
Six men, three of whom were tasered, were arrested and remain in custody at north London police stations.
The force said that during the arrests a 17-year-old boy, who was not part of the gang involved in the robbery, was also tasered.
A force statement said: "He was treated at the scene by London Ambulance Service but did not require hospital treatment.
"An inspector at the scene spoke to the teenager to check on his welfare and apologise for the incident.
"The Directorate of Professional Standards have been informed of the incident as is routine."