Majority of IRA arsenal came from Libya and US

The IRA is believed to have kept secure much of its arsenal since it announced the second ceasefire in 1997, though some of it was secreted away following a split in the ranks that year.

A large percentage of the arsenal was acquired from Libya during the 1980s, though some of it was smuggled in from the United States in the '70s and early '80s.

General John de Chastelain has revealed no details of what has been put beyond use.

However, the estimated IRA arsenal, prior to the first act of decommissioning was:

Semtex: 2.6 tonnes.

Detonators: 500.

AK-47 Assault rifle: 600.

Armalite AR-15 Assault rifle: No more than 20.

RPG-7 Rocket launcher: 11.

SAM-7 Surface-to-air missile: nine (never used, possibly because of defects).

LPO-50 Flamethrower: 6.

Webley .455 Revolver: 60.

7.62mm FN MAG

Machine gun: 12.

Ammunition hundreds of thousands of rounds, some still in manufacturers boxes.

The IRA is thought also to have acquired various other types of heavy machine guns, assault rifles, handguns, pistols and hand grenades over the years. Various explosive substances were also in the dumps.

IRA bomb makers became highly skilled in producing homemade explosive devices, particularly deadly mortar bombs.

Even the IRA's own leadership may not know the full extent of its arsenal, a leading expert on decommissioning said yesterday.

Sean Boyne, a defence analyst with Jane's Information Group, said British security services had been trying to keep track of the organisation's weaponry for decades.

They provided General de Chastelain with detailed estimates of armaments including SAM missiles, flame-throwers, machine guns, and explosives in 1998, and updated the figures last year.

But Mr Boyne said they could only roughly describe the arsenal the IRA had accumulated from various sources over the years.

"Nobody could be totally accurate. Maybe not even the IRA know all the weaponry its members have around the place.

"There could be some stuff hidden and forgotten that might turn up later."

According to Mr Boyne, who is publishing a book on decommissioning later this year, the 1998 estimates were primarily made up of arms supplied by Libyan leader Colonel Gaddafi during the 1980s.

Libya later supplied British officials with details of the shipments, allowing reasonably accurate figures to be prepared once seizures had been taken into account.

Mr Boyne said: "General de Chastelain has talked about some updated estimates that the security services gave him last year, but I can't imagine they would have changed that much."

Apart from Libya, some of the IRA's weapons came from the US during the 1970s, although shipments largely ceased from the mid-1980s, according to Mr Boyne.

Some armaments had been taken from the IRA's stocks by dissidents who formed the Real IRA, making it more difficult to assess the arsenal.

"We simply don't know how much went to the Real IRA," said Mr Boyne.

"The security services have made their estimates based on intelligence, and that is the best they can do."