15-year-old boy was killed after being hit by car near Pordenone.

An American soldier is under house arrest at the Aviano US air force base in Italy's northern Fruili-Venezia region where she faces accusations of fatally hitting a 15-year-old boy with her car, allegedly while intoxicated.

The 20-year-old female soldier reportedly had four times the legal driving limit of alcohol in her system when the accident took place near Pordenone at around 02.30 on Sunday morning, investigative sources told Italian news agency ANSA.

The soldier allegedly hit the boy when she lost control of her vehicle after speeding around a roundabout in Porcia, crashing into a group of teenagers on the bicycle path and catapulting the victim about 10 metres through the air on impact.

The 15-year-old, Giovanni Zanier, later died of his injuries. He had been on his way home from a disco with his friends and was wheeling a bicycle along the bike path, reports La Repubblica newspaper.

The soldier reportedly attempted to provide assistance and remained at the scene until emergency services arrived. After being detained by local police she was released into the custody of the US army, Italian media reports.

The road where the accident occurred was not illuminated, due to recent cost-cutting measures by the local council, however police say the lack of lights would probably not have averted the crash.