Anti-ceasefire republicans have stolen up to 30 high-powered rifles with telescopic sights that can be used in sniper attacks against the security forces in Northern Ireland, the Guardian has learned.

The theft of the long-range rifles has raised the spectre of a new lethal sniper campaign similar to the one the South Armagh Provisional IRA conducted that resulted in the deaths of several soldiers and policemen in the 1990s.

A security operation is still ongoing in the Irish Republic to track down the weapons, which can hit a target from over half a mile away and are normally used to shoot deer.

In 1997, British soldier Lance Bombardier Stephen Restorick died after being hit by a high velocity bullet fired from a sniper's rifle near the border with the Republic.

The Garda Siochána has confirmed that their officers in County Wicklow are investigating the theft of firearms during a break-in at a gun dealer's premises in Ashford on 8 September.

The Guardian has learned that up to 30 rifles with telescopic sights may have been taken in a highly organised robbery at the gun shop in the town. It is understood only two of the weapons taken have been recovered so far.

Security sources in Northern Ireland say the gang behind the break-in was organised by a terror unit controlled by the late Real IRA commander in Dublin, Alan Ryan.

He was shot dead in the same month following a dispute with armed non-political criminals in the Irish capital.

They say the fact that almost all of the weapons are still at large is causing a major security headache on both sides of the Irish border. The guns have been handed over to a new self-styled IRA which is an amalgam of the Real IRA, Republican Action Against Drugs and various armed dissident republican units in Tyrone, Derry, Armagh and Antrim, the security forces say.

In the Republic, Garda sources are linking raids over the last fortnight in the greater Dublin area to a desperate attempt to recover the rifles before they are smuggled across the border.

The two guns that have been recovered were found in north Dublin a fortnight ago during a "tailing" operation directed at associates of Alan Ryan who have vowed to take revenge against the Dublin crime gang behind his murder.

However, it is not expected that the long-range rifles would be used in the continuing feud between republican dissidents in Dublin and one of the city's most notorious group of gangsters.

One man was arrested in connection with the robbery of the rifles and released after questioning. A file is being prepared for the Republic's Director of Public Prosecutions.

Police believe the gang who broke into the shop at the Coolawinna Business Park used an electronic jamming device to disable an alarm signal from the shed used to house the business.

Gun dealers throughout the Irish Republic are being contacted to ensure that their premises are secure.

However, most gun dealers use conventional "dual-com" alarm systems which use landline telephone and GSM back-up phone signals. The robbers of the Wicklow gun dealer cut the phone line and jammed the GSM signal with the electronic blocker.

In the past organisations such as the Real IRA have tried to smuggle in such high-powered rifles from dealers in eastern Europe but their last attempt to buy weapons in Lithuania was thwarted and two men were arrested following a "sting" operation involving the British secret security services.

It is believed the dissidents have now opted for the "safer" option of stealing the high-powered hunting rifles, which are almost compatible with military rifles, from the legitimate Irish dealers.

A car used in the robbery is believed to have been stolen from south Dublin in the weeks before the robbery.

Asked about the theft of the weapons, a spokesman at Garda headquarters in Dublin said the break-in happened between 12.45am and 2.35am.

"It is believed at least five people were involved in the burglary, in which a number of firearms were stolen. The scene was preserved for a Garda technical examination."

He said a car was stopped three days later in Dublin. "During the course of the search Gardaí discovered two firearms which had been reported stolen."

A 26-year-old man was arrested and investigations were continuing to establish if the firearms were taken during the burglary.

The Garda press office did not confirm or deny whether other weapons were still missing, or specify the number that had been stolen.