LAGOS, NIGERIA - Nigerian rebels attacked an oil installation in the country's main producing region only after President Umaru Yar'Adua's offer of an amnesty, the group said Friday.

Militants from the Movement for the Emancipation of the Niger Delta (MEND) said in a statement they attacked an oil well late Thursday after an army raid on a village.

MEND accused Nigerian troops of launching a "punitive expedition" against the village of Abeti, in Delta State on Thursday evening, just after the president's amnesty offer.

"Their mission was to seek the homes of perceived militants and raze them to the ground ahead of any amnesty," the MEND statement said.

The militants said they had blown up a well-head in the Afremo field in Delta State and that the facility was owned by Royal Dutch Shell.

A spokesman for the Anglo-Dutch oil giant told AFP that the facility was operated by local company Sahara Oil, but was close to a Shell installation. Yar'Adua on Thursday offered Niger Delta militants the amnesty to try to halt attacks on the oil industry that have cut the country's production by a quarter over the past three years.

He said the amnesty would be given to any fighter who lays down his arms.

But the group made it clear weeks ago that it would not accept the president's amnesty offer but would continue what it has called its "oil war" launched on June 7.

MEND said in their latest statement that the army "lacks discipline and nurses hatred and seeks revenge for their humiliating defeat."

Since May, a combined police and army joint task force has been trying to drive the rebels out of the heart of the country's lucrative oil industry, which has been riven with violence since 2006.

MEND stages regular attacks on oil installations. It has demanded a fairer share of oil wealth for locals in the Delta region.

Its activities have badly hit Nigeria's oil output, cutting daily production from around 2.6 million barrels in 2006 to some 1.8 million barrels now.

Even before news broke Friday of the latest attack, the markets did not appear convinced by the president's amnesty offer. In New York Thursday, oil prices rose back above 70 dollars after news of an attack by MEND at dawn on Thursday.

MEND said an attack on Thursday was intended as a warning to Russia not to invest in the country's oil and gas industry, just after Russian President Dmitry Medvedev signed a series of major energy investment deals during a brief visit to the country.

"This is the fate that awaits the gas pipelines you plan to invest in (in) Nigeria if justice is not factored in the whole process," MEND said in a statement addressed to Medvedev.