The main militant group in Nigeria's oil-rich Niger Delta has issued new warnings of possible violence, after recent bombings of major oil pipelines in its campaign against the industry.  The Movement for the Emancipation of the Niger Delta, or MEND, says it destroyed two pipelines in the past two days and plans to attack a key oil storage facility.

The Movement for the Emancipation of the Niger Delta is retreating from direct confrontations with the now better armed and motivated Nigerian military.  Instead, the militant group is targeting oil pipelines in the Niger Delta in response to a military offensive launched four weeks ago.

On Friday, militants blew up the Otunana oil well and its gas lines.  And 24 hours later, they said the Makaraba oil well and gas facilities were destroyed.  The next target, MEND says, is the Chevron tank farm in Escravos and has issued warnings to workers at the facility to leave.

President Umaru Yar'Adua has defended the government's ongoing crackdown on militants in the Niger Delta.

"Developments recently in the Niger Delta region over the past few weeks, have necessitated the federal government's decision and decisive action against armed criminal elements who have hijacked genuine agitations in the region and constituted themselves into very serious threats to Nigeria's security and economic survival," Mr. Yar'Adua said.  

Mr. Yar'Adua has come under pressure to deal with the Niger Delta crisis, and has endorsed the biggest military offensive in the Niger Delta. But the Nigerian oil industry remains very vulnerable.

Militants have an easy target in the industry's network of pipes spread out over a vast wetlands region.  Pipelines that carry crude from wells to export terminals are prone to sabotage.  The attacks have cost the government and company several billions of dollars in oil revenues in the past few years and worsened environmental pollution.

Since the 1970s, Nigeria, Africa's top oil producer, has pumped more than $300-billion worth of crude from the delta, according to government figures.  But high unemployment, environmental degradation due to oil and gas extraction, a lack of basic resources such as fresh water and electricity have angered some of the region's youth and incited them to take up arms.

President Yar'Adua says the violence is hampering the implementation of the administration's development agenda for the region.

"Our agenda for resolving the lingering development challenges in the Niger Delta is on course," Mr. Yar'Adua said.  "However, we recognize that the provision of the necessary infrastructure for the socio-economic development of the area is fully dependent on an enduring atmosphere of peace and stability."

Since it emerged in the early 2006, MEND, which says it is fighting for a larger share of Nigeria's oil revenue to go to local people, has cut Nigeria's daily oil production more than 40 percent.