The main militant group in the oil-rich Niger Delta has called off its cease-fire with the Nigerian government.
The moves deals a potential death blow to a presidential amnesty programme aimed at ending violence that has crippled production in the West African nation.
The Movement for the Emancipation of the Niger Delta (MEND) issued a statement saying it would no longer abide by the unconditional October 25 cease-fire President Umaru Yar'Adua had negotiated with the group.
The militants warned oil producers with pipelines and personnel working in the creeks and swamps of the Delta that it would wage an "an all-out onslaught" against them.
The MEND "warns all oil companies to halt operations as any operational installation attacked will be burnt to the ground," the statement read. "Oil companies are responsible for the safety and welfare of their workers and will bear the guilt should any harm come upon their staff in the event of an attack."
The group added: "Nothing will be spared."
Militants in the Niger Delta have attacked pipelines, kidnapped petroleum company employees and fought government troops since January 2006.
They demand that the federal government send more oil-industry funds to Nigeria's southern region, which remains poor despite five decades of oil production.
That violence has cut Nigeria's oil production by about one million barrels a day, allowing Angola to surge ahead as Africa's top oil producer. However, Nigeria remains the third largest supplier of crude oil to the US, offering the country nearly a million barrels a day in November, according to US government statistics.
MEND announced it had brokered an unconditional cease-fire with the Nigerian government on October 25, but later said it broke the agreement to attack a pipeline December 19. The group said it attacked the line due to the long absence of Yar'Adua, who remains in Saudi Arabia receiving medical treatment for what his doctor described as a heart condition. Militants have questioned whether the amnesty programme Yar'Adua promised them -- which included cash payments to former fighters -- has been frozen in his absence.
