A 16-year-old girl was punched in the eye by a stranger who pounced on her close to a church.
The attack happened in daylight on Saturday evening near the Jesus Christ Centre at Conniburrow.
The offender approached her from behind, grabbed hold of her arm and punched her in the face.
The teenager tried to defend herself and kicked him in the leg, which allowed her time to run away.
She has described the offender as black, between 5ft 8ins and 5ft 9ins, muscular, with hair in an Afro-style, prominent cheek bones and dark brown eyes which have a yellow tinge to the white.
He has a small scar on the right side of his upper lip, and even stubble across his face.
He was wearing a navy blue original Adidas jacket with white collar and cuffs. There were white stripes running down the arms of the jacket and a white logo on the chest. He was also wearing black skinny jeans with a thick black belt, and also silver jewellery on his right hand middle finger.
The victim sustained grab marks to her left arm and bruising to her right eye were she was punched. She did not require hospital treatment.
Investigating officer PC Harry Bissett, based at Milton Keynes police station has appealed for witnesses to the attack, which happened between 6.30pm and 6.45pm.
He said: “This is a random attack on a young girl by an offender who was completely unknown to her, and it has had a big effect on her and knocked her confidence.
“If anyone has any information as to the identity of the offender, I would urge them to come forward and contact the Thames Valley Police Enquiry Centre on the non-emergency number 101.
PC Bissett added: “If you don’t want to speak directly to the police, you can contact the independent charity Crimestoppers anonymously on 0800 555 111. No personal details are taken, information is not traced or recorded and you will not go to court.”