BELFAST, Northern Ireland – The Irish Republican Army instructed its members yesterday to give up violence and embrace peace. The unprecedented statement also ordered IRA units to abandon their weapons.

The Provisionals’ leadership said the organization would pursue a democratic strategy and give up the armed struggle in which it murdered 1,800 people during three decades of the Troubles.

Prime Minister Blair praised the move as “a step of unparalleled magnitude” but Ulster’s unionists said it failed to address the IRA’s vast criminal empire and did not meet their demands for photographic evidence of weapons decommissioning.

The IRA’s statement said: “The leadership of Oglaigh na hEireann (the IRA) has formally ordered an end to the armed campaign. This will take effect from 4pm this afternoon. All IRA units have been ordered to dump arms.”

Sinn Fein/IRA’s goal of forcing the British out of Ulster and achieving a united Ireland would be done through “purely political and democratic programs through exclusively peaceful means,” the statement said.

Despite anger over the murder of Robert McCartney this year and the $50 million Northern Bank robbery last year, there was no specific mention of the IRA ending its involvement in robberies, punishment beatings, money laundering, smuggling, and its refusal to recognize the Police Service of Northern Ireland.

However, Mr. Blair interpreted a passage saying that “volunteers must not engage in any other activities whatsoever” as a pledge to end criminality and expressed hope that the statement would lead to the restoration of the Northern Ireland Assembly.

But the Democratic Unionist leader, Ian Paisley, indicated that a return to a devolved administration involving unionists and Sinn Fein remained a very distant prospect.

Mr. Paisley, the leader of the province’s largest party, said: “They have failed to explicitly declare an end to their multimillion-pound criminal activity and failed to provide the level of transparency that will be necessary to truly build confidence that the guns have gone in their entirety.”

The DUP’s mistrust of the statement was intensified by the one-sided concessions made by unionists during the peace talks. Unionists believe that steps such as the release of terrorist prisoners, the replacement of the RUC by the Police Service, and the creation of unaccountable all-Ireland bodies have not been reciprocated by republicans. In addition, it was revealed last night that, as part of the bargaining that led to the IRA statement, IRA murderers on the run are to be offered an amnesty that will allow them to return to Northern Ireland.

The IRA promised to cooperate with the Independent International Commission on Decommissioning and to invite a Catholic priest and a Protestant minister to witness the dumping of its armory.

But the refusal to include a photographic record of acts of decommissioning angered unionists, who were still smarting from the release this week of Sean Kelly, the IRA bomber who murdered nine people on Shankill Road, Belfast, in 1993.

Previous decommissioning acts did not convince unionists that the IRA was making a genuine effort to disarm.

In October 2003, David Trimble, who was then the leader of the Ulster Unionist Party, refused to deal with Sinn Fein because a decommissioning report by General John de Chastelain, the head of the international commission, lacked detail. General de Chastelain is on standby in the Irish Republic preparing for the IRA to dump its arsenal.

The IRA statement was issued as a DVD, which showed it being read by Seanna Walsh, who served a jail term for explosives offenses. As expected, there was no commitment to disband the IRA. It repeated the IRA’s view that the use of violence had been “legitimate.”

President Bush welcomed the “important and potentially historic statement.” The Irish prime minister, Bertie Ahern, also welcomed it but regretted that it did not include an apology to the victims of IRA violence that accounted for half the 3,600 deaths during the Troubles.

All three leaders stressed that words had to be backed by action. Mr. Blair said that only then would yesterday be regarded as “the day when finally, after all the false dawns and dashed hopes, peace replaced war and politics replaces terror.”

Firm evidence that the IRA was sincere would lead to the withdrawal of more troops.