Mr Ahern confirmed the presence of these individuals when giving his first comprehensive response to Thursday’s terrorist attack in London.
Later, reliable sources within Government indicated that the number of people kept under surveillance is very small, perhaps five individuals in all.
Mr Ahern said the Government takes its responsibilities in this regard very seriously and that those being monitored are al-Qaida sympathisers.
There are individuals living in the Republic of Ireland that we have to attach huge importance to and we do. This week underlines that and we do that under international co-operation and that’s a very important feature of it.
“People say that Interpol and normal security co-operation [between countries] are not necessary. They encroach on sovereignty and all these issues. But it is in the interest of every citizen in the world that people co-operate in security,” he argued.
Defence Minister Willie O’Dea said he was satisfied that intelligence specialists within the gardaí and army were “monitoring these individuals closely and fully”.
The disclosure came as Mr Ahern told reporters he had sent a message of sympathy to British Prime Minister Tony Blair on what he described as a “dark and terrible day in London” caused by callous and indiscriminate acts of terrorism.
He also confirmed that he will sign the book of condolences at the British Embassy in Dublin this morning.
He reiterated Ireland’s own security precautions and emergency response plans were adequate to deal with such eventualities.
“The National Security Committee, when any act happens [such as] yesterday, immediately makes sure we watch anything we are suspicious of. We watch the airport, we watch movements. There are a number of other security issues that the gardaí and army engage in. We do that as a matter of course. I spoke to them overnight and there’s no particular issue that they are any more concerned about than they would normally be. But obviously the alert is heightened,” he said, adding that strong security procedures are in place on some embassy buildings in Ireland.
Asked if a heightened risk would now apply to Shannon Airport, the focus for anti-war activists, Mr Ahern said he did not think so.
Turning to the London bombing, Mr Ahern said it now seemed clear from intelligence reports that the bus explosion was the first suicide bombing in Britain.
That fact would bring a whole new dimension to the security situation, he reasoned.
With strong rumours that the IRA is about to issue a definitive statement signalling its disbandment, Mr Ahern discounted that the London atrocity would affects its implementation.