Detectives are investigating a spate of robberies in and around Horwich town centre on New Year's Eve and New Year's Day.
Between 2.10pm on 31 December 2012 and 4.55am the following morning six people were targeted.
The first incident happened on Rock Street when a 45-year-old woman was pushed to the ground and had her mobile phone stolen by two thieves.
One offender was described as aged between 16 and 17, 5ft 8in tall, of slim build with black jogging bottoms and a dark grey hooded top. A second offender was wearing dark jogging trousers.
About 12 hours later, at about 2.15am on 1 January 2013, a 19-year-old man was placed in a headlock, threatened with a knife and robbed of his wallet on Penine Road, Horwich.
One offender is described as white, over 5ft 8in tall, with short ginger hair and wearing a grey hooded top. The second offender who was armed with a knife was white, about 20 or 21 years old, 5ft 8in tall with short black hair and wearing a dark blue jumper.
At 3am, a 19-year-old man was told he would be stabbed if he didn't hand over his belongings on Victoria Road, Horwich.
An offender is described as white, clean shaven, about 5ft 9in tall, with very short brown hair and of slim to medium build.
Between 3.15am and 4am, two 17-year-old teenagers were threatened with a knife and robbed of their wallets and other belongings on Victoria Road, Horwich.
The offender is described as white, 6ft tall, between 18 and 23-years-old, of slim build, and wearing a dark grey hooded top with blue stripes down the arms. He was in company with others.
The final robbery occurred between 4am and 4.10am on Chorley New Road near to St Joseph's School. A 15-year-old boy was placed in a headlock and robbed of his bag.
The offender is described as white and was wearing a grey hooded top and tracksuit bottoms.
Detective Constable Andy Devine, said: "We believe a small number of people, possibly no more than two or three, may be responsible for this spate of robberies on New Year's Eve and Day.
"They have not thought twice about targeting local residents who were out and about or on their way home following the celebrations.
"If you have overheard someone boasting about these offences, saw anything or have any information about who is responsible, please call us."
Anyone with information is asked to call police on 101, 0161 856 5763, or Crimestoppers, anonymously, on 0800 555 111.