An ethnic militia group in Nigeria's southeastern oil region vowed on Tuesday to attack oil workers there unless their companies shut down operations within three days.
The Niger Delta People's Volunteer Force (NDPVF) accused multinational oil companies including Royal Dutch/Shell and Italy's Agip of assisting the federal government's security forces in recent military operations against it.
The organisation claims to be a rebel movement seeking a better deal for the Ijaw people, the largest tribe in the Niger Delta which accounts for most of Nigeria's oil production. But the government says it is nothing more than a criminal gang which finances itself by stealing oil from pipelines and selling it clandestinely to tankers offshore.
After a meeting of its commanders on Monday, the NDPVF declared all-out war on the government. It said a new offensive dubbed "Operation Locust Feast" would begin on 1 October, the 44th anniversary of Nigeria's independence.
"Oil facilities will not be attacked since it will endanger the environment, but oil company personnel will be targeted," Moujahid Dokubo-Asari, the group's leader, told IRIN by satellite phone.
Nigeria is the world's seventh largest oil producer, with all of its 2.5 million barrels a day coming from the Delta region and nearby offshore oilfields.
On Tuesday international oil prices shot to more than $50 a barrel for the first time as traders fretted over possible disruptions to supply.
But the Nigerian armed forces and multinational oil companies operating in the Delta shrugged off the declaration of war.
"It's an empty threat," military spokesman Colonel Ganiyu Adewale said. "Progress is being made in the campaign to flush out the hoodlums, and the military is there to contain them."
Royal Dutch/Shell said it was taking precautionary measures in light of the militia's threat but would not be leaving the region and Agip also said it had no plans to relocate employees.
Dokubo-Asari's supporters see him as a Robin Hood-style robber hero, taking on the might of Nigeria's federal government on behalf of the local Ijaw population.
The Ijaws are the majority tribe in the Niger Delta and are thought to number eight million. They and other ethnic groups in the Delta, including their arch-rivals the Itsekiri, are cross that they have derived little benefit from the oil bonanza on their doorstep.
|Ijaw militants loyal to Dokubo-Asari stand guard|
Nigerian officials say Dokubo-Asari is little more than gangster who has used stolen oil to arm his men with sophisticated weaponry.
But political analysts believe that he and a rival gang leader in Port Harcourt, called Ateke Tom, may have high-level political connections. They suspect their gangs evolved from groups of political party thugs formed during the run-up to last year's elections.
The Nigerian military launched its latest offensive against the NDPVF in late August after the group claimed responsibility for a series of raids on Port Harcourt, the main operating centre of Nigeria's oil industry.
On Tuesday, Dokubo-Asari accused the Nigerian subsidiaries of Royal Dutch/Shell and Agip of "colluding with the Nigerian state to commit acts of genocide against our people". He said the firms provided logistical support to the military, including helicopters and topographical maps.
Agip officials denied assisting security forces in their offensive against the NDPVF offensive. This has included the bombing of several settlements and towns in the Delta, considered by the government to be rebel camps.
Shell also dismissed the allegations, pointing out in a statement that maps generated from its oil exploration activities are published as a statutory requirement.
"Our aircraft and facilities are for our operations. It's not true we're helping the government" Shell spokesman Donald Boham told IRIN on Tuesday.
Although both companies have pledged to stay put in Nigeria, the recent upsurge in violence in the Delta has led them to take some additional precautions.
Last week Shell said it had withdrawn "non-essential" workers from two oil facilities after it noticed troop movements nearby.
And on Tuesday Shell announced it was shutting down a facility pumping 28,000 barrels per day in the troubled area because it was not safe for workers to go there to rectify a fault.
Dokubo-Asari has said his fighters will only put down their weapons if President Olusegun Obasanjo calls a "sovereign national conference" to discuss ceding greater control of oil resources to the Delta's inhabitants and giving them more political autonomy.