A Police Service of Northern Ireland spokesman said it was treating as sectarian the petrol bomb and paint bomb attack on a loyalist housing estate close to the Bogside area of Derry at the weekend.
The devices were thrown into the Fountain estate from Bishop Street by a group of youths, some of whom wore masks, just before midnight on Saturday. No one was injured and no houses were damaged in the incident.
The estate has been subjected to petrol bomb and paint bomb attacks on more than 30 occasions during the summer.
Last week Sinn Féin's chief negotiator and MP Martin McGuinness said such attacks were wrong and unacceptable.
The attacks came as a town in Co Tyrone recovered from sectarian clashes that left seven police officers injured and resulted in the arrest of four people.
A riot broke out in Castlederg as members of the Protestant Black Preceptory passed through the nationalist Ferguson Crescent area of the town while Tyrone GAA supporters celebrated their All-Ireland quarter-final victory over Dublin.
The PSNI said one of their officers suffered a broken cheekbone as they tried to break up the disturbances.