THE US and its allies last night massively stepped up security at airports and large cities amid fears of an al-Qa'ida revenge attack following the killing of Osama bin Laden.
Hours after US President Barack Obama announced that Bin Laden had been killed, officials warned of repercussions.
CIA director Leon Panetta warned: "Though Bin Laden is dead, al-Qa'ida is not.
"The terrorists almost certainly will attempt to avenge him, and we must -- and will -- remain vigilant and resolute."
Security for Mr Obama's visit to Ireland later this month has also been stepped up.
Warnings of possible revenge attacks came after a remarkable day. It was revealed that the man who had waged war on the West in such spectacular and deadly fashion in New York and Washington on September 11, 2001, had been killed.
Bin Laden was discovered in a compound in Abbottabad, 35 miles north of the Pakistani capital Islamabad, with few outward-facing windows and no internet or telephone access, and killed after an operation that lasted 40 minutes.
There were reports he had used his own wife as a human shield in a last desperate attempt to save his own life before he was gunned down by US special forces.
Ruthless to the very last, his last act was to force his young bride to sacrifice her life as he tried to fire back at the US Navy Seals storming the compound.
While many experts had suggested the al-Qa'ida leader may have been hiding in Pakistan, it was assumed it would have been in the wild tribal areas close to Afghanistan and not in the centre of a garrison town that is home to thousands of Pakistani troops.
The operation on Sunday night, which was carried out by helicopter-borne US special forces, followed a months-long intelligence operation in which the CIA had monitored the three-storey residence around the clock. They had been alerted to it after monitoring the movements of a man suspected of being a courier for Bin Laden.
The helicopter-borne assault on the compound in Abbottabad was carried out with such clinical precision that the Seals, carrying Bin Laden's body, were on their way back to base within 40 minutes of landing.
Pictures from inside the house showed bloodstains on the floor next to a bed. Officials said that one of Bin Laden's wives, one son and two other men were killed. No photographs of Bin Laden were released but officials in Washington said some were taken.
Officials also revealed that Bin Laden's body had been buried at sea, after being washed according to Islamic tradition.
Garda and US security agencies had already drafted a tight security operation for Mr Obama's visit here later this month. But the threat of an assassination attempt has heightened as the international network of terror seeks revenge for Bin Laden's death.
There is no intelligence indicating that a threat is likely to emerge from sympathisers of al-Qa'ida or associated groups living here during the president's brief stay.
On August 20, 1998, American warships anchored in the Arabian Sea launched no less than 66 cruise missiles which obliterated a series of terrorist training camps near Khost, just inside Afghanistan's border with Pakistan.
THE death of Osama bin Laden in a shoot-out in his Pakistani compound is, in the first instance, a triumph for the United States and the presidency of Barack Obama. It marks the end of a pursuit which lasted almost 10 years from September 11, 2001, the date of the most spectacular act of terrorism ever committed.