A nail bomb and a blast bomb were thrown at the RUC during disturbances on the flashpoint Ardoyne Road this evening and two officers were slightly injured.
A police spokeswoman says large crowds are gathering in the area.
The violence follows the death of a Protestant teenager in a hit-and-run incident and today’s loyalist violence outside a Catholic primary school in north Belfast.
The RUC this afternoon launched a murder investigation into the death of 16-year-old Mr Thomas McDonald.
He was hit by a car which mounted a footpath in the city's Whitewell area, where rival crowds stoned and petrol bombed each other just hours earlier.
It happened three miles from the Holy Cross Catholic Primary School, where Protestant protesters have tried to block Catholic children from walking to school.
The death provoked threats of more serious disturbances. A family friend of the dead boy said: "It will be an eye for an eye."
Police later arrested a 32-year-old woman and were questioning three others in connection with the incident.
The RUC have refused to confirm it was investigating a sectarian motive for the incident, which comes after fresh clashes between loyalist protesters and security forces outside Holy Cross Primary School in the Ardoyne district.
But it is understood the car entered the loyalist White City estate after a stone was thrown at the vehicle as it emerged from the nearby nationalist Longlands estate.
RUC Det Supt John Brannigann said: "It's a tragic incident happening on an interface which has witnessed sectarian strife over recent times and I would obviously appeal for calm and restrain following this incident".
PA