Ministers warned of a new wave of Irish Republican bomb attacks

London: IRA dissidents are plotting a major bombing campaign to tear apart the Northern Ireland peace process, intelligence chiefs have warned.

Ministers have been warned that splinter groups such as the Continuity IRA are on the verge of a wave of killings. The security services said they believed a new generation of Republican fanatics were intent on exploding a lorry bomb on the mainland as well as killing Ulster Protestants.

Senior government sources said they had been alarmed by intelligence coming out of the province in recent weeks showing that dissident groups had acquired high quality detonators capable of killing on a mass scale.

Ministers were told that an attack by dissidents was all but inevitable in Northern Ireland this year.

Security forces have been placed on a high state of alert since Irish police thwarted a car bomb attack to coincide with the Unionist marching season earlier this week.

Five men were arrested and four cars seized south of the border after intelligence was received that a car bomb was to be driven into Northern Ireland — the same method used in the Omagh atrocity in 1998 which killed 28.

Senior sources said a hard core of Republican men in their 20s and 30s were building bombs using designs pioneered by the Provisional IRA. A senior Northern Ireland source said: "The threat from Republican terrorism is on the rise. There is now a significant threat of an attack this year. It is only a matter of time before they are successful".

"They are clearly overcoming some of the technical problems with detonators. There is a very real risk of a large-scale dissident attack. They are very active," he said.

Security chiefs at likely targets around the UK said they had been warned to redouble precautions against a potential lorry bomb attack.

Canary Wharf and the Houses of Parliament have both been considered as likely targets, but security chiefs also said they feared an attempt to emulate the 1984 Brighton Bomb attack on the Conservative Party conference.

Those preparing for the Conservative conference in Birmingham in October have factored the threat into security preparations.