A 20-year-old Polish woman was attacked by three men who punched her in the face as she was walking to work.
The incident happened at around 6am on Saturday, October 23 near the junction of Blackburn Road and Willows Lane in Accrington.
The men then stole the woman's white Samsung Avila mobile phone worth £65 and ran off in different directions.
Detective Inspector Claire Holbrook, of Accrington CID, is appealing for witnesses.
She said: "At around 6am Saturday, October 23 a 20-year-old Polish female was walking to work and talking on her phone near to the junction of Blackburn Road and Willows Lane when she was subjected to an unprovoked assault by three males who punched her in the face. Fearing for her safety the girl has thrown her phone away believing that the men wanted her phone."
She added: "The men then stole the phone. All three males are described as white 5'8" tall all and around 20/23 years of age wearing dark clothing."
Anyone with information whould call Accrington CID on 01254 353741 or on 0845 1 253545 or via Crimestoppers anonymously on 0800 555 111.