The Garda and anti-terrorist police in Britain last night foiled what Metropolitan Police officers said was an attempt to bomb London "within minutes" by republican dissidents associated with the Sinn Fein breakaway group, the 32 County Sovereignty Committee.
Nine people were arrested in co-ordinated swoops in London, Dublin and Dundalk.
In a joint operation by the Metropolitan Police and MI5, three men, believed to be students from Dublin, Co Kildare, and Co Louth, were arrested in possession of ready-made incendiary devices after officers received information from the Garda about the movements of known republican dissidents.
A fourth person, a woman, was arrested near Oxford Street, and later a man and a woman were taken into custody at Euston Road, near the British Library.
Security sources indicated the men were thought to be members of the dissident republican group, the 32 County Sovereignty Committee..
Two of the men were arrested at about 4.30 p.m. yesterday in Thomas Doyle Street, in the south-east of London, and a third man was arrested at the same time in Gower Street, close to Tottenham Court Road, in the West End of London. No shots were fired during the arrests.
The British Prime Minister, Mr Tony Blair, last night described the operation as "very important and successful". He said it reflected the close co-operation between the security forces in the UK and the Republic.
The Taoiseach, Mr Ahern, complimented the Garda and praised the effective co-operation of both security forces.
It is understood the men tried to dispose of the explosive devices when approached by police.
In a statement last night, the head of Britain's Anti-Terrorist Branch, Mr John Grieve, said the arrests came after a "prolonged investigation" into dissident republican terror groups who were planning an "imminent . . . terrorist attack" in London. He said his officers believed the explosive devices "were intended to be used in London within minutes".
Further arrests were expected last night as police searched a number of addresses in London.
Commuters travelling home during the rush hour were caught up in the operation to arrest the men when a large part of central London surrounding Gower Street and Tottenham Court Road was sealed off.
The men arrested in London were aged between 18 and 25 and one of them is from Dundalk. Garda sources confirmed their suspicions about possible joint republican operations after a 34year-old man was arrested in Dundalk yesterday. He was arrested under Section 30 of the Offences Against the State Act. He is from the town and well known to gardai. Last night he was in custody in Dundalk Garda station.
The man was arrested as a result of a series of planned searches of houses and flats in Dundalk which led to the recovery of arms and a quantity of bomb-making equipment. A shotgun and a sawn-off shotgun found in the search were said to be in excellent condition.
Garda sources confirmed that the sawn-off shotgun, shotgun and ammunition recovered may have been intended for "ordinary" crime.
In Dublin, a man and a woman were arrested shortly after 5 p.m.