Nigerian President Umaru Yar'Adua has ordered a military offensive to curb the rising mayhem in the oil-rich Niger Delta. The action comes days after oil rebels attacked a key petroleum facility in the region. Gilbert da Costa has more for VOA in this report from Abuja.

The president's spokesman, Segun Adeniyi, told reporters that a major military crackdown in the troubled Niger Delta is inevitable as the government seeks to halt the spiraling violence.

A Nigerian separatist militant levels his machine gun at reporters from his war boat on the Escravos River in southern Nigeria (File)

"While the federal government remains fully committed to rapid resolution of problems and grievance of the people of the Niger Delta, it will not shirk its responsibility for law and order, as well as the safety of lives and property in the Niger Delta and all other parts of Nigeria. Militants in the region who continue to spurn the peace overtures of the federal government must be prepared to face the full consequences of taking up arms against their fatherland," he said.  "The federal government will take all necessary action to stop criminals from willfully depriving the region of this indispensable ingredient of development."

The planned military offensive comes after Delta rebels stormed the offshore Bonga oil fields operated by Royal Dutch Shell, in the vast wetland region which has all of Nigeria's oil, resulting in the company's decision to cut output by 200,000 barrels per day.

The most powerful rebel group in the region, the Movement for the Emancipation of the Niger Delta, has claimed responsibility for the attack and promised further raids on the oil industry.

The group has made the release of its presumed leader, Henry Okah, who is currently on trial for treason, a pre-condition for suspending its campaign of violence.

At peak production levels, Nigeria can pump around 2.6 million barrels of crude daily, but attacks by militants have cut production by 25 percent.

Delta rebels say they are fighting for control of the region's oil wealth, but their fight is intertwined with communal and ethnic rivalries in the delta, where kidnapping for ransom, extortion and oil theft are also big business.

Despite the rising tensions, the government says constructive dialogue with local communities will continue.

Authorities have acknowledged that poverty and neglect lie at the root of many of the Delta's problems. Recent measures to try and foster development in the region have failed to quell discontent.

Nigeria has lost its status as Africa's leading oil producer to Angola since April and at least one Western oil company, Total, is reviewing its future operation in Nigeria due to the violence.