Petrol bombs were thrown by youths in the Nailors Row area during two nights of violence on Sunday and Monday, while police officers responding to the trouble were also attacked.Two boys aged 13 and 14 were arrested for suspected riotous behaviour, but there are concerns that children even younger were involved.Chief Inspector Jon Burrows said: "The children involved are between 10 and 14 years of age and I want to make it very clear to parents they need to exercise parental responsibility."We will be advising social services on every occasion that we arrest a young person involved in this type of street violence."The disorder started in the wake of last weekend's Bloody Sunday commemorations and nationalist youths from the Bogside area of the city have been blamed.But it is feared dissident republicans are behind what's happening.Councillor Gary Middleton of the DUP said: "There are sinister elements behind those and that's clear and everyone knows that people are putting these young people up to this."Unfortunately it's the young people who have to suffer the consequences with criminal records in years to come."Sinn Féin deputy First Minister Martin McGuinness has also condemned the incidents.He tweeted: "Disgraceful that children as young as ten involved in attacks on our neighbours in the Fountain estate, Derry. Parental control essential."Police said Tuesday night was quiet with no reports of further trouble in the Fountain, however they have stepped up their patrols of the area.Meanwhile the two boys arrested on Sunday have been released on bail pending further inquiries.