There was more rioting in the mainly Catholic Short Strand area of east Belfast last night.
A police officer was injured in the second night of street violence on an interface between loyalist and nationalist areas.
The police say petrol bombs and other missiles were thrown at them and one officer was injured.
The PSNI said he was hit in the face with a missile but that calm was restored at about 2.30am this morning.
Three people were arrested for riotous behaviour, possession of petrol bomb and disorderly behaviour.
They are helping police with their enquiries.
East Belfast Area Commander Chief Inspector John McKeag said it was totally unacceptable and the PSNI would bring those responsible before the courts.
He has set up a team to ensure that and said he is confident of more arrests.