Updated

The Olympic flame flew first class Saturday to Northern Ireland for a five-day tour that includes a visit to the Republic of Ireland capital, Dublin, and features heightened security to ensure that Irish Republican Army factions don't spoil the celebrations.

The Protestant and Catholic leaders of Northern Ireland's unity government welcomed Olympic officials as the flame landed at Belfast City Airport. The flame spent its first two weeks on British soil traveling through England and Wales, then much of Saturday on the Isle of Man midway between Britain and Ireland.

Olympic officials had to receive special permission to carry a live fire on board an aircraft. The symbolic spirit of the London Games was kept in four lanterns secured into two front-row seats on the British Airways chartered flight, watched over by a firefighter.

Paul Deighton, chief executive of the London Organizing Committee of the Olympic Games, carried one of the lanterns to First Minister Peter Robinson, the British Protestant who leads the Northern Ireland government, and his Irish Catholic colleague, Deputy Minister Martin McGuinness. Their 5-year-old coalition is the centerpiece of a successful peace process still facing occasional assaults from IRA die-hards in several small groups.

Both leaders said they expected the Olympic tour to shine a spotlight on how far Northern Ireland has come since the major rival paramilitary groups — most notably McGuinness' own Provisional IRA — ceased fire in the mid-1990s, greatly reducing the bloodshed over this British territory.

"We are privileged to welcome the flame to Northern Ireland and to witness its journey ... past many of our iconic landmarks, creating what promises to be a once-in-a-lifetime spectacle for all to see," Robinson said.

But the torch's ambitious itinerary through every corner of Northern Ireland, and its arrival during United Kingdom-wide celebrations marking Queen Elizabeth II's 60th anniversary on the throne, also pose a particular security headache for police working to keep IRA die-hards at bay.

Underscoring the threat, a suspected IRA activist tossed a grenade at a police unit Saturday in Northern Ireland's second-largest city, Londonderry, where the Olympic cavalcade will spend parts of Monday and Tuesday. The police, who were searching a property at the time, weren't injured but their vehicle suffered heavy shrapnel damage.

In Belfast a police deputy commander, Assistant Chief Constable Alistair Finlay, said the Northern Ireland public would see heavy deployments of officers both along the Olympic torch routes and at events associated with the queen's Diamond Jubilee events. He told a press conference at police headquarters that IRA splinter groups "will take any opportunity to cause disruption."

He said people might find roads blocked, and other unexpected security delays, to ensure that the IRA factions' opportunities to plant bombs or hoax devices near Olympic routes were minimized. "We are taking these steps to keep communities and their officers safe. We would not do this if it was not absolutely necessary to protect life," Finlay said.

But he said the deployment of so many police officers also would present the anti-British militants plenty of opportunities to attack their "principal target," police officers themselves.

The first of more than 400 Northern Ireland torchbearers will depart Sunday at dawn beside Belfast's newest tourist attraction, a landmark Titanic exhibition on the same dockside where the doomed liner was constructed a century ago. The torch and its accompanying convoy of media and support staff is scheduled to stop at the grand Stormont Parliamentary Building, center of the power-sharing government, on a hill overlooking the city.

The second and third days in Northern Ireland see torchbearers run past several points associated with the most savage atrocities of the Northern Ireland conflict, staying overnight in Londonderry.

While the torch isn't supposed to travel outside its host country, the Olympic procession starts day four in Dublin. The Irish successfully lobbied for the political concession to highlight today's strong British-Irish relations. That day ends back in Belfast for a major circuit of the city and a party outside Belfast City Hall.