A 12 and 14-year-old boy were approached by a man from behind who demanded money and a mobile phone.
The older boy refused and was hit in the face.
The younger one was robbed of an amount of money and the suspect then ran off towards Lytham Close.
Police have now released the details of the incident, which happened at about 3.30pm on Inglemire Lane on Monday, January 25, and appealed for witnesses.
The suspect has been described as white, around 5 feet 6, wearing a dark grey hooded top and a white bandana over the bottom half of his face.