The RUC is investigating an explosion on the Belfast-Dublin railway line in the Carnagat area of Newry, Co Down. The explosion happened at 1.20 a.m. yesterday after the RUC received several telephone warnings that a bomb was on the line.
It was the second day that rail services had been disrupted. An RUC spokesman said the caller claimed to be from "the south Down IRA".
Rail services between Portadown and Dundalk have been cancelled, with buses ferrying passengers to their destination. A spokesman for Northern Ireland Railways, Mr Roger Hope, said it "regretted" having to cancel the services but decided to take the precaution until the RUC decided it was safe to reopen the line.
Mr Hope said NIR appeared to be the "victim" of political events in Northern Ireland, with people seeing the rail service as an "easy method of protest".
The recent bomb scares and protests have had a damaging impact on rail services. Last year, two trains were removed because of disturbances in July.
Bomb disposal experts are also examining a suspicious object left on the line between Lake Street and William Street in Lurgan, Co Armagh, on Wednesday, which was discovered by rail workers.
The RUC was also investigating a security alert in Banbridge, Co Down, after receiving a telephone warning that a bomb had been left in the town.
Meanwhile, in Derry, a 90-yearold woman was one of six elderly people who escaped injury in two separate overnight petrol-bomb attacks on Catholic-owned homes in the Waterside.
Ms Bridget King and three other members of her family were unhurt after two petrol-bombs were thrown at her Victoria Road cottage just after 1 a.m. yesterday. A car was heard speeding off in the direction of the nearby loyalist village of Newbuildings immediately after the incident.
Just over an hour later, the home of Mr Tommy Grimes and Ms Grace Grimes, both in their 70s, was extensively damaged when two petrol-bombs were thrown through their livingroom window in Curlew Way, in the mainly Protestant Shearwater Estate.
"We have the best of neighbours, all of them Protestants, and one of them saved our lives last night," said Mr Grimes. "He heard the crash and alerted us to the fire and, thank God, Grace and me got out."