A pipe bomb exploded in north Belfast tonight in an attack believed by the police to have been carried out by loyalists.
The device exploded in the mainly Catholic Hillman Street in the Duncairn area.
A spokesman for the Police Service of Northern Ireland (PSNI) said there were no reports of injuries and an army bomb disposal team was sent to the scene.
Meanwhile, four men were still being questioned by police after incidents in Derry believed to be linked to dissident republicans.
The four, all from the west bank of the Foyle in the city, were being held at Lisburn police station after two security operations in separate parts of Derry.
Police said they made the arrests after stopping a car which had been acting suspiciously on the Foyle Bridge.
Items were also recovered from the vehicle, said a PSNI spokesman.
A police source said detectives were investigating a possible link to a bomb scare on the outskirts of the city, which started about the same time last night. It is also being linked to dissident republicans.