An email purportedly from the Movement for the Emancipation of the Niger Delta (Mend) said it was responsible for the ambush in southern Nigeria on Friday.

BBC: Nigerian 'Mend' militants claim Niger Delta ambush

The Movement for the Emancipation of the Niger Delta (MEND) is an insurgent group that demands compensation from petroleum companies for the pollution and deaths they have caused.

CENTERFORSECURITYPOLICY: Nigeria in flux

So, Ofeibea, the group that's holding the oil workers is called the Movement for the Emancipation of the Niger Delta, and it's fairly new in Nigeria, but well organized, I gather.

NPR: Nigerian Authorities Seek Release of Contractors

Kidnappings of expatriate oil workers in the Niger Delta region by the Movement for the Emancipation of the Niger Delta (MEND) earlier this year have also increased concerns surrounding the security of the county's energy infrastructure.

CENTERFORSECURITYPOLICY: Dragon at the fount of Africa

The Movement for the Emancipation of the Niger Delta (MEND), the main rebel group fighting for political autonomy and local resource control in the oil-producing Niger Delta region, has called off its unilateral ceasefire, just weeks after announcing the move.

ECONOMIST: A big rebel group in the Niger Delta calls off its ceasefire

And Nigeria is one of the biggest suppliers of oil to the United States, which explains why the attacks by a group calling itself the Movement for the Emancipation of the Niger Delta, has been blamed for rising oil prices around the world.

NPR: Militant Group Targets Oil Producers in Nigeria

Last month, the Movement for Emancipation of the Niger-Delta (MEND) -- an ethnically-based militia operating in Nigeria's oil-rich southern region -- launched "Operation Dark February" (which carried over into March), promising to bring about an "Armageddon in the Nigerian petroleum history".

CENTERFORSECURITYPOLICY: Nigeria ablaze