DUBLIN, Ireland —The Ulster Volunteer Force, an outlawed Northern Ireland group that for decades attacked the province’s Catholic minority, yesterday renounced violence and pledged to disarm.

The breakthrough in Northern Ireland’s 13-year-old peace negotiations came just five days before the formation of a new Catholic-Protestant government, the major goal of the Good Friday peace accord of 1998.

The UVF’s elder statesman, 73-year-old Gusty Spence, told a Belfast news conference that the paramilitary group would formally cease to exist at midnight.

Mr. Spence — who was convicted of the UVF’s first murders in 1966 — said the organization he founded that year “will assume a nonmilitary, civilianized role.”

“All recruitment has ceased. Military training has ceased. Targeting has ceased, and all intelligence rendered obsolete,” Mr. Spence said. By intelligence, he was referring to the UVF’s files on potential targets.

He added that UVF units had been “deactivated,” while the group’s weapons supplies “have been put beyond reach” of most UVF members.

This means that UVF weapons have been placed in secure locations known only to senior UVF personnel but have not been presented to Northern Ireland’s independent disarmament chief, retired Canadian General John de Chastelain. Mr. Spence said he expected talks between UVF representatives and Mr. de Chastelain to begin soon.

Nearly 13 years ago, Mr. Spence was chosen to read out the UVF’s decision to call a cease-fire and to express “abject remorse” for the innocent Catholics it had killed.

Britain’s secretary of state for Northern Ireland, Peter Hain, welcomed the UVF move as further evidence that the province was “emerging into a new and positive era.” But he said the UVF must surrender its arsenal as proof of its intent.

“Of course, everyone is judged on what they do as well as what they say. There must be delivery. There must be [weapons] decommissioning,” Mr. Hain said.