Last night the security forces were attempting to establish whether the attack was the work of the IRA. The possibility could not immediately be ruled out that the blasts were the work of a small breakaway republican group.
In any event the attack represented a body-blow to hopes of getting a renewed peace process off the ground.
The bombs, thought to contain together around 1,500lbs of explosives, were driven in two vehicles through the main security checkpoint of the barracks. The bombing clearly represents a major security lapse given that the IRA ended its ceasefire last February. Despite this, security in Northern Ireland has never been tightened to previous levels.
The army base is a huge sprawling complex in which many hundreds of military personnel work and where hundreds of families live. As the Army's HQ in Northern Ireland it attracts a considerable flow of both military and civilian traffic in and out of the base.
The first bomb exploded at 4.30pm several hundred yards inside the base and it was followed by the second, smaller explosion close to the Army medical centre where the injured from the first bomb were being ferried.
An Army spokesman said: "We can confirm that there were two vehicle-borne explosions within Thiepval Barracks
"The first was in a car park close to the administrative building manned mainly by civilian staff. The second appears to have been designed to catch casualties being taken to the medical centre, which has been badly damaged."
There appear to have been no warnings.
The blast also damaged a children's nursery as well as the garrison church and the Naafi family shop. Medical teams and first-aid trained soldiers were on the scene within moments.
It was later revealed that an eight-year-old girl was among the nine blast victims taken to Lagan Valley Hospital. A spokesman said she had escaped major injury. Six men and three women were admitted to the hospital and two, described as major casualties, were later transferred to the specialist head injuries unit at Belfast's Royal Victoria hospital.
Condemning the bombing as "wicked and unspeakable", and the placing of a second bomb as "barbaric", the Prime Minister said, after he arrived in Bournemouth for today's Conservative Party conference: "It is clearly a very serious development." But he added: "We have no reason to believe it is the Provisional IRA."
Sir Patrick Mayhew, the Secretary of State for Northern Ireland, who is attending a Northern Ireland economic conference in Pittsburg, Pennsylvania said it would be catastrophic if loyalists ended their ceasefire in response to the Lisburn bombs. He urged them not to be provoked, and to continue their "admirable self-discipline and restraint".
David Trimble, leader of the Ulster Unionists, told BBC television that loyalist paramilitaries should "not to join the IRA in their wickedness".
Republicans are likely to view the bombings - and the embarrassing security breach at what should have been one of Ulster's most secure installations - as a show of defiance after the security forces' recent successes against the IRA on the mainland. Hopes had been raised in recent weeks by reports of a possible new IRA ceasefire, but these have remained unsubstantiated.
One immediate theory is that the bomb, the first in Northern Ireland since the IRA ceasefire ended in February of this year, may represent an attempt to make the point that it is still capable of attacks on its home territory.
The explosions will in any event serve to place heavy pressure on the loyalist ceasefire. At the time of the explosion UVF prisoners in the Maze were meeting loyalist leaders to express doubts about the continuing cessation.
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