A man has been arrested in connection with a 1990 bomb attack that killed four people in county Armagh.
The 55-year-old man has been arrested by detectives from PSNI Legacy Investigation Branch.
Detective Inspector Deborah Eakin said: “The male was detained in Armagh this morning on suspicion of a number of offences including the murder of three police officers and a Catholic nun in an explosion on the Killylea Road in Armagh on 24 July 1990.
“He has been taken to the Serious Crime Suite at Musgrave Police Station in Belfast for questioning.”
Constable William Hanson, Reserve Constable Joshua Willis and Reserve Constable David Sterrit were killed in the blast.
Sister Catherine Dunne, were killed when a landmine located at a culvert on the Killylea Road Armagh was detonated on the July 24, 1990.
Another woman was also seriously injured in the blast.
At the time it was reported that the three uniformed members of the RUC were killed instantly when their unmarked patrol car ran over and detonated an explosive device, two miles south of Armagh.
The blast lifted the car over a high hedge into a field, where it landed on its roof.
The nun and another woman were in a car going in the opposite direction when they were also caught by the blast.
The bomb, believed to have contained at least 1,000 pounds of explosives, left a 20-foot crater in the road.