Witnesses saw boy hit girl's hands as she clung to balcony before falling to her death.

The juvenile court of Bologna on Thursday confirmed the arrest of a 15-year-old boy accused of killing his 13-year-old former girlfriend in the north Italian city of Piacenza.

The boy, currently detained in a juvenile jail in Bologna, was arrested after the girl, Aurora, fell to her death from the seventh-floor balcony of her apartment building on Friday.

Prosecutors and Carabinieri police officers allege that the boy pushed Aurora over the balcony and, as she clung desperately to the railings, he hit her hands repeatedly to make her fall.

The girl fell about 10 metres onto a terrace three floors below, Corriere della Sera reports.

The boy, who was found in possession of a 15-cm long screwdriver, told police that Aurora's death was the result of suicide, a claim dismissed outright by her family and friends.

"He threw her down, she wasn't crazy, or depressed, she was yet another victim of violence" - Aurora's sister wrote in a public outburst on social media - "He was obsessed with her, she tried in every way to get rid of this reject."

The boy was arrested after several people told police they witnessed him pushing Aurora off the balcony, according to Corriere della Sera.

Other witnessses came forward to say they saw the boy assault Aurora on the street in recent weeks, providing investigators with photographs and video footage of the incident.

Aurora's funeral will be held at Piacenza Cathedral next Tuesday.