Northern Ireland Office Minister Paul Murphy also welcomed the news, but stressed the need for the cessation of violence to be maintained.

IRSP executive member Willie Gallagher: "A position of complete ceasefire"

The republican INLA announced the end of its 23-year campaign in Northern Ireland on Saturday.

The news came hours before tens of thousands of people gathered to pray for Omagh's dead and injured.

Mr Ahern said it was "good news at the end of a bleak and tragic week".

The statement was read by Willie Gallagher, of the IRSP

The Real IRA which bombed Omagh, killing 28 people, "must now convert a suspension of operations into a cessation of violence," he said.

Two of the three hardline guerrilla groups opposing the agreement have since declared a truce, including the Real IRA.

Mr Ahern urged the last group, the Continuity Army Council or Continuity IRA, to follow suit.

In a statement by the INLA's political wing, the Irish Republican Socialist Party (IRSP), the group said it had instructed all its units to desist from offensive actions.

It said it accepted the conditions for armed struggle did not exist.

While the group continued to oppose the Good Friday Agreement, it recognised that the political situation had changed since its formation.

BBC Ireland Correspondent Mark Devenport: It acknowledges the desire for peace

The armed struggle could never be the only option for revolutionaries, the statement said.

The INLA statement said: "We acknowledge and admit faults and grievous errors in our prosecution of the war.

"Innocent people were killed and injured and at times our actions as a liberation army fell far short of what they should have been.

"For this we as republicans, as socialists and as revolutionaries offer a sincere and heartfelt apology."

INLA: "The conditions for armed struggle do not exist"

The INLA, seen by many as one of the most ruthless and unpredictable republican groups, has been under pressure to end its campaign of violence.

The announcement now means only one paramilitary organisation, the Continuity IRA, is not on ceasefire.

The Real IRA, which apologised for the Omagh bomb, declared its own truce on Tuesday.

The INLA was established in 1975, recruiting many former members of the official IRA.

The group murdered Conservative Northern Ireland spokesman Airey Neave when a bomb was left under his car at Westminster in March 1979.

Billy Wright: Murdered by the INLA

The organisation was also responsible for one of Northern Ireland's worst atrocities in which 17 people were killed at the Droppin' Well pub in Ballykelly, Co. Londonderry, in December 1982.

In December last year, the INLA murdered loyalist LVF leader Billy Wright at the Maze prison.

Ulster Unionist MP Ken Maginnis told BBC News 24 he welcomed the statement.

Ulster Unionist MP Ken Maginnis: The inevitable outcome of democracy

He said every movement in such a direction was a movement towards political stability in Northern Ireland.

Mr Maginnis said: "The words of this statement are to my mind are an admission of the futility of violence.

"And I feel that the whole thing is the inevitable outcome of the overwhelming force of democracy in relation to the agreement that was reached on 10 April."

He said there was a movement towards political stabilty in Northern Ireland.

He said: "What a pity that we had the events of Omagh last Saturday when we see what can be achieved."