Police blamed loyalists for the attack on the house at Carnany, in Ballymoney, County Antrim, which they condemned as "sickening and brutal murder".

BBC correspondent June Kelly: There is an air of disbelief

Richard Quinn, 11, Mark, nine, and eight-year-old Jason were brought up as Protestants and attended a Protestant school. Their mother is a Catholic.

The attack came hours before Northern Ireland's Parades Commission refused a new Orange Order application to march down the nationalist Garvaghy Road at Portadown.

Orangemen have been in a stand-off with security forces for a week in protest at the original decision to ban them.

Police outside the house where the brothers died

Two men and a woman who were also in the house managed to escape and were being treated in hospital.

A police spokesman said: "A neighbour reported hearing a loud bang outside the house just moments before the flames were spotted."

Officers on patrol nearby arrived on the scene "within moments" but were beaten back by the intensity of the blaze.

Two women described how they heard Richard Quinn crying for help.

"I got out to the house and all you could see was smoke. You couldn't have seen anything," said one.

"One of the wee ones was upstairs - Richard. I tried to get up twice but I couldn't, the heat and smoke was that bad."

'Future of peace'

UK Prime Minister Tony Blair said the arson attack was "an act of barbarism".

Mr Blair said: "Evil and vicious sectarian murders must not be allowed to triumph over the clear will of the majority of right and good thinking people who want to pursue a future of peace for Northern Ireland."