A group of loyalists smashed 17 cars parked outside a girls' Catholic school in north Belfast earlier today.
A police spokesman said six men, two of whom were armed, carried out the attack at the Lady of Mercy Secondary School in the predominantly Protestant Ballysillam area.
One of the men stood guard at the entrance to the school, while the other five smashed the cars. Police officers were at the scene, which is around half a mile from Holy Cross School in Ardoyne.
There were no injuries during the incident.
Sinn Féin's Mr Martin McGuinness, who was visiting the Ardoyne area, said the latest attack has brought people to the point of despair.
"Everybody concerned with the education of our children has to be appalled and disgusted by this unacceptable deterioration of the situation."
Some parents took their children away from the school, many vowing to keep them at home tomorrow.
Mr McGuinness added: "Yesterday was bad enough and I think there was some hope that common sense would prevail, that people would see the importance of real and honest dialogue to resolve the problems that existed.
"But the later escalation of all of this had I think sent people almost to the point of despair."
He called on politicians and community leaders in north Belfast to do everything in their power to bring an end to the violence.
In yesterday's violence, gangs of up 500 nationalists and loyalists attacked police lines into the early hours of the morning.
A Police Service spokesman said today that the renewed trouble was sparked by a row on a footpath between a Catholic woman collecting her daughter from the school and a Protestant woman.
Police moved in to quell a confrontation that developed, but it escalated into serious disturbances. Over 400 police and British soldiers were eventually deployed.
However, loyalists claimed last night the trouble began after a wreath erected to commemorate the killing of a Protestant by repulicans was removed.
Police were attacked with petrol bombs, acid bombs and fireworks. A follow-up operation led to the discovery of three crates of ready-made petrol bombs and a can of petrol in the Brompton Park area.
At least 136 petrol bombs were thrown during the riots, one of which destroyed an armoured police car. Six cars were hijacked and set on fire while two buses were hijacked but later recovered.
Police said seven people were hit by the eight plastic bullets they fired, while four Catholic men needed hospital treatment after being wounded by shotgun pellets.
A schoolboy (13) was earlier taken to hospital after being injured when his school bus passed through the Ardoyne and was targeted by stone throwers.
Additional reporting by PA
