Police in Derry believe children as young as seven were involved in disturbances in the Bogside area of the city last night.
A crowd of around 20 to 30 youths, some masked, threw petrol bombs and other missiles at passing vehicles during trouble, which began at around 6.30pm.
A bus and a van were struck, although there were no reports of any injuries.
Up to ten petrol bombs were thrown and police came under attack when they responded to the disorder.
Officers liaised with community representatives and the area returned to calm around midnight.