Rebels from Nigeria's oil-producing Niger Delta said they had blown up a Royal Dutch Shell pipeline and killed 11 soldiers in a gun battle today, but the army denied losing any men.
The attack was the latest act of sabotage in a campaign by militants that has cut oil output in the world's eighth-largest producer by around a fifth since 2006, helping to drive global oil prices to record highs.
The rebel Movement for the Emancipation of the Niger Delta (MEND) said in an emailed statement that it had sabotaged the Shell pipeline at Awoba flow station in southern Rivers state in the early hours of Monday.
"Today's attack is dedicated to the administration of (President) Umaru Yar'Adua and (Vice President) Goodluck Jonathan who have failed after one year in office to ensure peace, security and reconciliation in the Niger Delta," it said.
Shell in Nigeria said it was investigating and had no immediate comment. Nigeria's army confirmed a blast at a Shell facility close to Awoba, which was not guarded by soldiers.
"The cause of the explosion has not yet been determined but it is strongly suspected that explosives might have been used by miscreants," Sagir Musa, army spokesman in Rivers state, said.
Musa said troops had been sent to the scene but denied that 11 soldiers in a military gunboat were killed in a shoot-out.
The campaign of sabotage in the delta, which began in early 2006, has prevented Africa's biggest oil industry from reaching its full potential.
Nigerian Oil Minister Odein Ajumogobia said he expected 175,000 barrels per day of oil production shut in by recent militant attacks to be restored in the coming weeks, but added almost half a million more remained affected by the insecurity.
"We had about 470,000 barrels per day shut in even before these (latest) incidents, which is a direct result of security issues," he told local television in an interview.
Shell was forced to shut in about 164,000 barrels per day of Bonny Light crude output late last month because of militant attacks in the delta, which it has since been restoring, although a force majeure remains in place for its Bonny Light exports.