That could impact heavily on Nigeria's oil production and its exports, the mainstay of its economy. The country, the most populous on the continent, is a key supplier of crude to the United States.
Output was slashed by 40 percent to around 2 million barrels per day before a government amnesty halted fighting in late 2009.
Fighting erupted in the delta in southern Nigeria two weeks ago following renewed insurgent attacks on oil installations as a government amnesty declared in July 2009 began to seriously unravel.
A Joint Task Force comprising Nigerian army, navy and air force personnel launched a large offensive two weeks ago, storming rebel camps and villages suspected of harboring insurgents.
Human rights activists claim that as many as 150 people, mostly villagers, have been killed. The government and the military have issued no casualty figures but insisted they were not targeting civilians.
Henry Okah, leader of the main insurgent group, the Movement for the Emancipation of the Niger Delta, warned Thursday that arms are flowing into the oil region where foreign oil giants such as Exxon Mobil, Chevron, Royal Dutch Shell and Total operate.
In a telephone interview from a prison cell in Johannesburg, South Africa, where he is awaiting trial on charges of deadly bombings in Nigeria's capital Abuja Oct. 1, Okah said the violence "is going to get much worse.
"The problems of the delta are still here, and as long as they remain unresolved it will dissolve into utter chaos."
Okah, who was allegedly involved in providing weapons to MEND in its early days, predicted that there will be a significant deterioration after presidential elections scheduled for January.
Nigeria's political barons who control the corruption-ridden electoral machine, are known to arm militant to intimidate voters among the country's 150 million people during election campaigns.
Okah said once the elections are over, the weapons distributed in the delta will be used to step up the violence and destroy oil facilities.
He was arrested in November in Johannesburg, where he has lived since 2009 after being freed in the amnesty, under South African anti-terror legislation. He denies involvement in the Abuja car bombings that killed 12 people on Nigeria's Independence Day, although MEND claimed responsibility.
"There's a rearming of most groups in the delta now," Okah said, but denied knowing the source of the weapons.
MEND has been fighting since 2006, demanding the government alleviate the intense poverty among the delta tribes and provide a more equitable sharing of Nigeria's oil wealth.
They also want the oil companies, who they claim are in cahoots with the military, to cleanup decades of untrammeled pollution in the region.
But in the main there's little to distinguish the militants from criminal gangs, who specialize in the wholesale theft of oil which is smuggled abroad, often by the tankerload. That practice, known as "bunkering," has made the gang chieftains -- and their political patrons -- rich on the spoils.
A cease-fire that followed the 2009 amnesty is seen to be crumbling daily, with a new rebel group known as the Niger Delta Liberation Front, composed mainly MEND diehards, leading the insurgency in the swamps and creeks of the delta.
The NDLF is led by John Togo, a hard-liner who was once a MEND general. He appears to be the main target of the military dragnet under way and three of his camps have been attacked in recent days. The group proclaimed its existence Nov. 15 and claimed a pipeline attack Dec. 5.
Thousands of MEND fighters, led by their commanders, surrendered their weapons during the amnesty in return for promises of government stipends and jobs. But many have gone on the warpath again, claiming the government had reneged on the agreement. These include a faction associated with Okah.
MEND claimed responsibility for attacks on offshore drilling platforms run by the British exploration company Afren and Exxon Mobil Nov. 8 and 14 in which 13 foreign workers were kidnapped at gunpoint. They were rescued when the military raided the rebel camp where they were being held.
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