Gainsborough's daughter is at the Tate

"It was quick in and out, they were just interested in those two (paintings)," said police spokesman Jim Molloy.

The intruders set fire to their getaway vehicle soon after the robbery and later failed in a bid to hijack a car at gunpoint, but it is believed they escaped the area.

Chief Superintendent Sean Feely said: "They fired a shot in an attempt to hijack a car, but the motorist refused to hand over his vehicle."

Police search teams are combing the area and conducting door-to-door searches, Molloy said.

IRA gang

A View of Florence by Belotto is thought to be worth around IR�1m (�777,000) and Gainsborough's Madame Baccelli: Dancer about IR�2m (�1.54m).

This is the third time that this Gainsborough work has been stolen from the Palladian-style stately home.

In 1974 an IRA gang that included British heiress Dr Rose Dugdale, stole 19 paintings, then valued at IR�8m.

Former Conservative MP the late Sir Alfred Beit, a member of the de Beers diamond family, was still alive at the time and living in the house.

Beit was abducted along with his wife during the robbery, but was later found unharmed and the pictures recovered.

In 1986 a 13-strong gang headed by Dublin criminal boss Martin Cahill, known as The General, stole 18 works of art.

I think its a tragedy for the art loving public and a tragedy for Lady Beit

Paul O'Kelly of Oisin Gallery

That robbery featured in the John Boorman film The General and included pictures by Vermeer, Goya, Rubens and the Gainsborough.

Outrage

All but three of the paintings turned up over the years in a variety of locations, including London, Belgium, the Netherlands and Turkey.

The Beit collection was handed over to the Irish nation in the 1990s and many of the works are on show at Russborough.

Raymond Keaveney, Director of the National Gallery of Ireland, described the theft as "an outrage".

Art experts believe the thieves may face difficulties disposing of the works.

One Dublin art expert said: "They are not sellable on the open market, maybe the thieves are hoping a reward will be offered."

Superintendent Feely agreed that the works are so well known that they will be difficult to sell.

But it is possible that the works were stolen to order for a private collection.

Though Russborough House has been open to the public since 1978, it is still the home of Sir Alfred Beit's widow, Lady Beit.

Chief Superintendent Feely said she was "in good form considering what has happened".

"I think its a tragedy for the art loving public and a tragedy for Lady Beit," said Paul O'Kelly, of the Oisin Gallery.