A number of homes have been evacuated in Londonderry after a suspicious object was left on a bus.
Northland Road has been closed between Branch Roundabout and Springvale Park.
Army technical officers have been to the scene.
Transport Minister Danny Kennedy condemned the incident and praised the "bravery" of the bus driver. "The driver showed immense courage under very difficult circumstances," he said.
"Attacks on public transport impact the entire community who depend on buses and trains to get to work, school, hospital and go about their daily business," he added.
Councillor John Boyle, of the SDLP, said the latest security alert was a "source of real distress" to people in the area.
"A suspicious object was left was a bus on the Northland Road area which is a main arterial route in and out of the city, maximising the disruption in Derry," he said.
"A number of families have been evacuated from their homes on one of the coldest night of the year so far, exacerbating their distress."
Councillor Eric McGinley of Sinn Féin said the disruption caused by the incident showed a "total disregard for the entire community".
"I would call upon anyone involved in this type of activity to desist; they are going against the will of the vast majority of the people in this area who have indicated that they want to move forward without this type of disruption," he said.