Dissident republicans were believed to be responsible for planting a bomb on a railway line close to a London train station early yesterday which prompted transport chaos across the city.
Amid condemnation from politicians, thousands of commuters were last night still experiencing severe delays as several London Underground stations remained closed as a result of security alerts.
Responding to the news, the Taoiseach warned that the threat from dissident republicans must be taken very seriously.
Speaking to reporters in Dublin, the Taoiseach said he had reports there were "quite a number of people involved, not anything like past times". He said these were "people who are determined to continue to undermine the good work of everybody", and great effort was being put into attempts to combat them.
He said the Minister for Justice, Mr O'Donoghue, and the British Home Secretary, Mr Jack Straw, had already planned to meet next week, and would now be discussing the threat from republican dissidents. He also hoped to meet the British Prime Minister, Mr Blair, before the end of July.
The Sinn Fein Assembly member, Mr Gerry Kelly, said if the devices found were indeed bombs they had clearly been planted by opponents of the peace process.
"The only effective counter to such activities is to demonstrate clearly and unambiguously that politics works. That means the promise of the Good Friday agreement and all subsequent negotiations needs to be implemented in full and without further delay," Mr Kelly added.
Early investigations confirmed the bomb, discovered shortly after 6.15 a.m. on a stretch of track close to Ealing Broadway station in west London, contained half a kilogram of high explosives.
It was destroyed in a controlled explosion, but it was not known whether the device contained Semtex. Metropolitan Police Deputy Assistant Commissioner, Mr Alan Fry, said police were investigating the possibility that the device was linked to an explosion on Hammersmith Bridge in June.
The Ealing bomb device was discovered after officers from the Anti-Terrorist Squad were informed that media organisations in Dublin had received a coded telephone warning at about 6.15 a.m.
Bomb disposal experts closed Ealing Broadway station and evacuated people living locally before searching the track. At 10.55 a.m. a bag containing the bomb was found.
As road traffic in much of west and central London was brought to a standstill and commuters were forced on to the roads, the organisers of the Queen Mother's 100th birthday pageant said they believed the bomb was intended to disrupt it.
The event went ahead as planned amid a large security presence.
The bomb alert caused severe disruption to travellers as the stretch of track forms part of the main western corridor out of London and thousands of people travelling to the west of England, Wales and Heathrow Airport were forced to make alternative arrangements.
Further problems were caused for commuters and tourists when security alerts spread throughout central London.
Security alerts at Victoria, Westminster and Acton Central Underground stations forced them to close and bomb disposal officers carried out a controlled explosion close to Horse Guards Parade and Westminster station at 1.30 p.m. a few hours before the Queen Mother's pageant was due to begin. However, the suspect package was later discovered to be an unattended bag.
In the House of Commons, the Northern Ireland Secretary, Mr Peter Mandelson, said it "certainly appears" the device was planted by dissident republicans and said he would be speaking to Mr O'Donoghue to discuss what further action could be taken to combat terrorism.
Speaking to MPs during Northern Ireland Questions, Mr Mandelson said those responsible for the bomb had used the same code word warning as in last month's attack on a railway line in Newry and in other bomb hoaxes and incidents in Britain. He also said the Ealing bomb was possibly similar in size to the bomb discovered at Newry.
Mr Mandelson said: "The main paramilitary groups are maintaining their ceasefires. There remains, though, a threat from dissident paramilitaries who are opposed to the Good Friday Agreement. I utterly condemn this threat and the disruption caused by the incidents today."