The move was described by military sources as a prudent precautionary measure. The authorities appear to have no definite signs that further IRA attacks are in the offing, but with the organisation's ceasefire at an end there can be no certainty that the London bombing represents an isolated incident.
Security sources said yesterday that men of the 1st Battalion of the Royal Irish Regiment based at Catterick, North Yorkshire, are expected to arrive within the next 48 hours.
In another response to the situation, two emergency meetings will be held to discuss ways of increasing national security and upgrading the protection of the royal family.
Police chiefs, and officers from MI5 and the Home Office are to meet in the next few days to review security measures throughout the country. They are particularly concerned about intelligence reports that the next bomb could be aimed at a target outside London.
Ministers said the redeployment of British soldiers on the streets of Belfast was based on security advice from the RUC Chief Constable, Sir Hugh Annesley.
The re-introduction of troops was clearly intended at Westminster as a signal to the IRA and the public in Northern Ireland that security reductions brought in during the ceasefire could be reversed.
It is understood the soldiers will be moved into border areas of Armagh and Fermanagh. A small number of army patrols are on the streets and soldiers have been re-issued with steel helmets and flak-jackets. Security at bases has been reviewed, and it is believed fortifications may be increased in a number of places.
Since the IRA ceasefire of August 1994 some 1,600 troops have been transferred out of Northern Ireland, leaving around 16,500 soldiers to carry out much- reduced duties. Around 5,500 of the troops are locally-recruited members of the Royal Irish Regiment.
"The troops were withdrawn, but they were never completely out of the picture," said one source. "The decision to send them back was a security decision, not a political decision. They are there to back up the police."
Meanwhile, ministers are seeking a compromise over demands by John Bruton, the Irish Prime Minister, for "proximity" talks before elections. London may seek to use a round of trilateral meetings between parties and ministers to meet that demand.
There was also hope that an agreed date for all-party negotiations after the elections could be announced to persuade Sinn Fein to announce a renewed ceasefire by the IRA.
Security talks, page 2