The surge in violence was heightened by a raid on an insurgent camp in the troubled Niger Delta region by government troops in what could be a precursor of a larger military offensive against rebels operating in the swampy southlands that hold most of Nigeria's oil.
The growing unrest comes amid a mounting power struggle between political barons in the Muslim-dominated north and the overwhelmingly Christian south in presidential elections slated for early 2011.
Amid this turmoil the discovery of a large shipment of Iranian arms, including 107mm rockets and 120mm and 80mm mortars, at the country's busiest port, Lagos, the commercial capital, Oct. 26 has raised fears that the insurgents may be getting weapons from the Islamic republic or elsewhere.
Iranian Foreign Minister Manouchehr Mottaki said the intended recipient of the arms, hidden in 13 shipping containers supposedly holding "construction materials," was another West African state but he has refused to name it.
The spate of recent attacks began with Oct. 1 car bombings in Abuja that killed 12 people. The Movement for the Emancipation of the Niger Delta, long the principal insurgent group, claimed responsibility.
On Nov. 8, MEND raided an oil platform operated by the British exploration company Afren 7 miles off the coast of Akwa Ibom state and kidnapped five foreigners.
The latest incident involving Exxon Mobil's platform in the Oso field took place Sunday. MEND claimed that attack, too.
Oso is one of Nigeria's biggest condensate fields and seven other platforms are also operating there, with an average daily output of 75,000 barrels per day.
Exxon Mobil said the platform that was attacked has shut down, cutting production at Oso by 45,000 barrels a day.
The insurgency, with the oil industry its primary target, broke out in 2005 with the impoverished and long-neglected southern tribes demanding a greater share of the country's oil wealth and protesting untrammeled pollution, including constant oil spills.
When the government declared a 90-day amnesty in mid-2009, insurgents had slashed oil production by 40 percent. Current output is around 2.1 million bpd, far below Nigeria's capacity.
The wholesale theft of oil by insurgents and criminal gangs associated with them -- and as often as not financed by political figures who use the gunmen for muscle at election time -- was costing the state $1 billion a year.
The recent violence has marked the end of the government peace initiative. The amnesty and subsequent cease-fire began collapsing with the incapacitation of President Umaru Yar'Adua earlier this year. He died of heart problems in May.
During the amnesty, insurgent commanders led thousands of their men out of the swamps to surrender their weapons.
But promised government stipends largely ended up in the pockets of government officials or senior insurgents. Jobs and training programs promised by the government failed to materialize.
The political feuding triggered by Yar'Adua's death and the upcoming elections have intensified the uncertainty across Africa's most populous nation, whose 150 million people are more or less equally split between Muslims and Christians.
The military, which has been unsuccessful in defeating the insurgents in the past, took the offensive following the Nov. 8 kidnapping at the Afren platform.
On Monday, troops hit jungle camps in Rivers State where the Afren employees were being held. According to reports from the region, the military hit the camps with rocket fire, some of which landed so close to the captives that they had to be moved to safer areas.
The recent MEND operations suggest the insurgents have new commanders with fighters shunning former chieftains such as General Boyloaf, Farah Dagogo and Government Tompolo, who have been given political sinecures and hefty payoffs by laying down their arms.
A new militant group, led by former MEND militants, declared itself Nov. 16. The Niger Delta Liberation Front is commanded by John Togo, a former MEND general.
The group claims it has nine former MEND chiefs and that its war against the oil companies like Exxon Mobil and Anglo-Dutch Shell is part of a wider campaign against a corrupt government.