LAGOS, Nigeria — Nigeria's main militant group declared a unilateral cease-fire in the southern oil region Sunday, ending the worst spate of militant attacks in years to hit Africa's oil giant.

The Movement for the Emancipation of the Niger Delta said it was ceasing hostilities immediately after appeals from elders and politicians in the region. Three years of attacks have cut Nigeria's oil production from 2.5 million barrels per day to around 1.5 million barrels.

The group said it would launch another spate of reprisal attacks in the event of another military raid on one of the group's base camps.

A military operation on Sept. 14 prompted the latest surge in violence, with rare clashes between the military and militants that normally avoid outright confrontation. The militants declared a state of war, but called it off Sunday.

"We hope that the military has learnt a bitter lesson. The next unprovoked attack will start another oil war that will be so ferocious that it will dim the pleas of the elders," the group said in an e-mailed statement.

The military unit charged with calming the southern region cautiously welcomed the development, if borne out.

"If that is true, I think it is a good development for themselves, the region, the nation and the international community," military spokesman Lt. Col. Sagir Musa told reporters.

"We are open to amicable resolution of this in-house crisis."

The group, which is a loose alliance of various armed gangs operating in the southern Niger Delta, attacked military positions, destroyed pipeline-switching stations and blew up pipelines that carry crude from wells to export terminals in southern Nigeria.

The state oil company said daily production is now down about 40 percent from Nigeria's normal daily output of 2.5 million barrels, helping send crude prices to historical heights this year in international markets.

The militant group emerged about three years ago, calling for more federally controlled oil-industry revenue to flow to the southern states where the petroleum is pumped.

The militants have focused their attacks primarily on the country's oil infrastructure, seeking to heighten pressure on the government.

Battles with the military are rare, but there have been several clashes over the past week, raising the prospects of a larger conflict or one that spirals out of control of the militant leaders or military to embroil the wider Niger Delta region.

That's the nightmare scenario for the international petroleum companies in Nigeria, which has Africa's largest oil industry, since it would leave the largely unguarded network of pipelines in tatters in areas where repairs would be impossible.