Four young children between the ages of 11 and 13 have been arrested after allegedly running down a 71-year-old woman in a stolen car before fleeing the scene.

Cecilia De Astis, a widowed grandmother, was fatally hit by an out-of-control vehicle while walking in the Gratosoglio neighbourhood of Milan on Monday.

Local police officers have arrested four children on suspicion of vehicular homicide aggravated by failure to provide assistance. The suspected driver of the vehicle was 13.

Witnesses told local police that they saw at least two of the children run away to a nearby Roma camp after the crash.

It was at this illegal camp at Via Selvanesco, just two kilometres from the incident, where officers reportedly arrested the children.