DUBLIN (AP) — Britain on Tuesday unveiled a new expert panel to investigate Irish Republican Army activities as a man was charged with possession of a Belfast trove of IRA weapons, underscoring the tensions that threaten to tear apart Northern Ireland's unity government after eight years of Catholic-Protestant cooperation.

Power-sharing, a central achievement of two decades of peacemaking, is at risk because of a killing that police and other authorities have blamed on the IRA. The underground organization, which killed nearly 1,800 people during a failed 1970-1997 campaign to force Northern Ireland out of the United Kingdom, was supposed to fade into history as part of the 2007 creation of a coalition combining former enemies from the British Protestant majority and the IRA-linked Sinn Fein party.

But while the IRA officially disarmed and renounced violence in 2005, splinter groups have continued to kill — and now, for the first time, the IRA itself stands accused of using lethal force in retaliation.

Police commanders say IRA members last month ambushed and shot to death an expelled comrade, Kevin McGuigan, in retaliation for his own alleged killing in May of a senior IRA figure, Jock Davison. McGuigan, who was shot in the arms and legs by the IRA more than a decade ago in a so-called "punishment" attack, had expressed bitterness toward Davison but denied involvement.

The three-member expert group is supposed to report to government leaders by mid-October on the state of the IRA today, including the open question of whether commanders ordered or permitted the McGuigan hit. If so, it would be the first confirmed killing by the dominant branch of the IRA, called the Provisionals, since the 2007 resurrection of power-sharing.

The experts also are tasked with assessing the current structure and activities of a half-dozen other paramilitary forces, including IRA splinter groups and anti-Catholic gangs. None of these are affiliated to any party in Northern Ireland's government, making their violence much less politically explosive.

Even when international weapons inspectors announced the Provisional IRA's total disarmament in 2005, analysts broadly agreed that the IRA retained firearms for defensive or community-intimidation purposes. The McGuigan killing, if confirmed to be an IRA attack, would offer the first concrete evidence of this.

The past decade of occasional bomb and gun attacks committed by breakaway factions already has demonstrated that IRA leaders lost control of portions of their arsenal, most importantly caches of the Czech-made plastic explosive Semtex, before it could surrender the weaponry.

A man was arraigned in a Belfast court Tuesday on charges of possessing about a pound (half a kilogram) of Semtex, two detonators, two handguns and 200 rounds of ammunition for use by an unspecified IRA faction. Kevin Dolan, 45, had been arrested Sunday in England following the weapons discovery in a house in Catholic west Belfast, a primary power base for the Provisional IRA and its rival offshoots.

Dolan offered no plea at Belfast Magistrates Court. He did offer a clenched fist salute to friends and family in the visitors gallery as police led him from the dock.