JK Signage crew erect a giant, five-storey-high photograph of US President Barack Obama on the side of The Gibson Hotel, Point Village, Dublin, yesterday. Martin Nolan
Garda and Army intelligence officers are concerned that activists, currently keeping a low profile in the UK or on mainland Europe, could come here to take advantage of US President Barack Obama's visit and launch an attack.
Both forces are keeping a close watch on contacts between sympathisers located here and activists overseas and are monitoring their movements, telephone and computer traffic.
A dozen hardline supporters of groups linked to the al-Qa'ida network pose the biggest headache for the security agencies involved in combating international terror threats on a daily basis.
The prime suspects are mainly people who have lived here for several years, and represent a tiny minority in the 40,000-strong Muslim community.
Their alleged role over the past decade has been in providing logistical support for active terror cells based elsewhere, including fundraising, supplying forged passports and identity cards and establishing safe havens for fighters on the run from other countries.
There has also been evidence in the past of suspected fighters being sent here for "a rest" before returning to a war zone.
The biggest fear for security chiefs is the emergence of previously unknown youths, who have been radicalised by hardliners.
One of the masterminds of al-Qa'ida terror plots in the UK was radicalised in Belfast while living in Dublin, although his training and instruction were gained elsewhere.
Mohamed Meguerba, an Algerian whose parents lived in Belgium, came to Dublin in 1997 and lived here for four years, marrying an Irish woman and living in Gardiner Street and Ranelagh.
He did not come to garda notice until he met a radical cleric during a trip to the North and his behaviour changed dramatically.
His wife became terrified of him and eventually left him. He went abroad on a false French identity card and travelled extensively, despite several arrests.
During one interrogation in Algeria he revealed details of the deadly ricin plot to poison hundreds of Londoners and also of his meetings with Bin Laden. His information led detectives to an address at Wood Green in London where they found original copies of the plotters' recipe for ricin and signs of an attempt to make it in a pestle and mortar.
Overall,there are are about 60 sympathisers under regular surveillance here. This group includes Algerians, Libyans, Egyptians, Moroccans, Tunisians and Pakistanis.
In 2004, the US accused a charity's Dublin office of helping to channel financial support to terror groups and named a man living here in Ballinteer, in south Dublin, as its Irish representative.
It claimed the Sudan-based organisation had been raising funds for Bin Laden and others.
The Irish representative, who has consistently denied any links to terrorism, lives openly here and has never been sought by the US authorities.
Most of the group under regular surveillance live in the greater Dublin area.
Meanwhile, security measures at the US and Israeli embassies and the homes of diplomats from the two countries will also be heightened.
Transport Minister Leo Varadkar last night said he did not believe Bin Laden's assassination would deter Mr Obama from visiting Ireland.
"All the security precautions have been taken and we're confident there will be no problems in that regard," he said.
Mr Varadkar also insisted he did not believe the killing would increase the risk of attacks here.
"The fact that Osama bin Laden is dead doesn't mean that the risk of al-Qa'ida has gone away. . . But we don't believe that Ireland is any more exposed than it was in the past."