Police have released a CCTV image of two men they wish to speak to in connection with a robbery at a petrol station in Milnrow.
The man waving the hammer demanded that the shop assistant open the till and both offenders pushed behind the counter and started filling a bag with cigarettes.
They then grabbed cash from the till and escaped down Dale Street towards Ladyhouse Lane.
The first offender is described as male, about 5ft 6in tall, slim build and wearing a dark coloured balaclava, dark top, dark tracksuit bottoms and white gloves with black fingers. He spoke with a Jamaican accent.
The second man was also about 5ft 6in tall, slim build and also wearing a dark coloured balaclava, dark top, dark tracksuit bottoms and white gloves with black fingers.
Detective Constable Hannah Greetham said: “Luckily the incident did not turn violent, but that is probably due to the compliance of the victim in this case.
“These men used aggressive language and threats of violence while brandishing a dangerous weapon at the shop assistant, who was left with little option but to comply to their demands.
“Due to their use of balaclavas we were not able to get a full description of these men, but they may well have removed their disguises having left the petrol station and that is when witnesses may have unwittingly seen what these men look like.
“Indeed, two people are seen to ride their pedal cycles past the garage at the same time as the offenders are fleeing across the forecourt.
“There is even some suggestion the offenders may have crossed over the border into Rochdale from Oldham, so they are not necessarily local to the area.
“They could be vital witnesses and we would urge them to come forward and speak to the police.”
Anyone with information is asked to call Police on 0161 856 8552 or independent charity Crimestoppers on 0800 555 111.