Nigeria's military condemned Sunday an attack on an oil pipeline in the Niger Delta that was claimed by an armed militant group.

The Movement for the Emancipation of the Niger Delta (MEND) said in a statement it had attacked the Agip-operated pipeline late Saturday, a week before governorship elections in the southern, Christian-dominated region of Bayelsa, the home state of President Goodluck Jonathan.

"The (military) condemns the attack in view of all that it portends for the region," a special Nigerian military force said in a statement.

The MEND group also threatened more attacks to "reduce Nigerian oil production to zero and drive off our land thieving oil companies".

Nigeria, already wracked by a series of deadly Islamic militant attacks and reprisals, is Africa's most populous nation and top oil producer.

The MEND statement gave no details on damage to the pipeline run by Agip, a subsidiary of Italian oil group Eni.

Lieutenant Colonel Timothy Antigha told AFP troops had not determined the degree of damage. There was no immediate reaction from Agip.

The armed MEND group said the "relatively insignificant attack" was to indicate its presence in the oil-rich region and "a sign of things to come," warning of more attacks, including against companies from South Africa.

More than 25,000 ex-militants from the region who surrendered their arms have been given payouts and vocational training under a government amnesty programme introduced in 2009.

The amnesty led to a significant reduction in militant attacks and an increase in the output of oil, Nigeria's economic mainstay.

"Unfortunately, people who were never part of the agitation have emerged and want to claim amnesty and its benefits by force," the Nigerian military said.

It also warned of collateral damage if "individuals and communities decide to provide sanctuary to these enemies of the society."

Gubernatorial elections are scheduled in Bayelsa state on Saturday, but the ruling party's decision to shut its doors against a former state governor who sought reelection is creating tension in the state.