Police are searching for four men who raided watches and jewels worth up to £750,000 from David M. Robinson jewellers in Altrincham yesterday.
The gang, dressed in dark jumpsuits and balaclavas, used axes to smash their way into the store at 12.30pm. They escaped in a Land Rover which was later found abandoned by the police.
Greater Manchester Police have confirmed that no one was injured in the incident.
Initial reports suggest the gang used a battering ram-type device to force open the front door, disabling a metal locking system. They then forced a security guard to the ground before smashing through a number of display cabinets, including one containing a selection of Rolex watches.
According to Safergems, staff immediately activated the security smoke system and attempted to close the roller shutters, however they were prevented from doing so by one of the offenders, who place a metal pole in the window.
Police have described the event as a planned and calculated heist.
David M. Robinson was previously targeted in 2010 when thieves drove a car into the front of the store to access a number of Rolex watches.