A crude bomb partially exploded on a railway line in Belfast on Saturday night as it was being examined by a British army technical officer.
The device was discovered under the railway halt at Finaghy on the outskirts of south Belfast after 11 p.m. when a man was seen acting suspiciously in the area.
An army bomb disposal expert was examining the device, using remote control equipment, when it partially detonated at 11.30 p.m., but he was not injured.
One man was arrested at the scene and another taken into custody later in a follow-up operation by the RUC.
They were both helping police with their inquiries yesterday.
A police spokesman said those who left the bomb had shown "complete disregard" for local residents and people drinking in a pub 100 metres away.
It is not yet known what quantity of explosives was contained in the device which was undergoing technical examination yesterday.
A suspect object was also discovered on the railway line in Lurgan, Co Armagh yesterday morning.
The area around Lake Road was sealed off for most of the day as army technical officers examined the scene.
There was also a bomb alert in Newry on Saturday evening when three armed and masked men hijacked a bus in the Derrybeg area shortly before 6 p.m.
They ordered passengers off before forcing the driver to take the bus to the town's Court House.
The area was evacuated and bomb disposal experts carried on a controlled explosion on a device left on the bus.
It was later declared "an elaborate hoax".