Northern Ireland politicians are condemning a car bombing outside a courthouse in the city of Londonderry.
The device exploded Saturday night as police, who had received a warning, were evacuating the area. There are no reports of injuries.
The Police Service of Northern Ireland posted a photograph of a vehicle in flames and urged the public to stay away.
More than 3,700 people died during decades of violence before Northern Ireland's 1998 peace accord. Most militants have renounced violence, but some Irish Republican Army dissidents carry out occasional bombings and shootings.
Uncertainty about the future of the Irish border after Brexit is adding to tensions. John Boyle, who is mayor of the city also known as Derry, said violence "is the past and it has to stay in the past.