Armed militants in Nigeria's southern oil region seized nine foreign hostages, damaged an oil export terminal and blasted a major crude oil pipeline in simultaneous weekend attacks that reduced the country's oil exports by at least 20 percent.

Militants of the Movement for the Emancipation of the Niger Delta (MEND) claimed responsibility for seizing nine foreign oil workers during a raid on a barge on Saturday morning belonging to U.S. oil service company Willbros on the Forcados River in the delta.

In an email, the militant group which claims to be fighting for local control of oil wealth in the impoverished oil region, gave the names and nationalities of the hostages including three U.S. nationals, a Briton, two Thai nationals, two Egyptians and a Filipino.

MEND also said it damaged Shell's Forcados oil export terminal, ruptured a major oil pipeline belonging to the oil giant near its Chanomi Creek oil pumping station and another gas pipeline belonging to the state-owned Nigerian Gas Company.

Shell spokesman in Nigeria, Donald Boham, confirmed the attacks and damages, saying the company has been forced to suspend crude oil exports from the Forcados terminal that handles an average of 400,000 barrels a day.

"We can't load crude at Forcados until the damage is repaired," he said.

Shell said in statement it evacuated and shut down its EA oil platform in shallow offshore waters where the militants seized four foreign workers in January. The hostages were freed unharmed after 19 days in captivity after President Olusegun Obasanjo rejected the militants' demands for the release of Moujahid Dokubo-Asari, a delta militia leader facing treason charges, and Diepreye Alamieyeseigha, a former oil region state governor detained for corruption.

MEND said the latest attacks were in direct response to air attacks by the Nigerian military on ethnic Ijaw villages in the delta on Wednesday and Friday. The Nigerian military had said the attacks targeted barges used by criminal gangs to siphon crude oil from pipelines in the delta for sale to accomplice vessels waiting offshore.

Security agencies say the illegal trade in crude oil is the source of funds for armed groups flourishing in the oil region in recent years. Nigeria estimates losses at times to amount to as much as 10 percent of its daily exports of 2.5 million barrels a day to the illegal trade.

Obasanjo on Saturday met with top security officials, governors from the oil region and Shell Nigeria managing director Basil Omiyi, to work out ways "to ensure that the nine hostages are freed unharmed.through dialogue," Information Minister Frank Nweke said in a statement.

The President "wishes to reiterate that criminal activities such as kidnappings and hostage-taking in the region can only retard and impede the implementation of plans and programmes for the benefit of the generality of the people," the statement said.

More than 15 years of restiveness in the oil-rich delta, where impoverished locals accuse successive Nigerian governments and oil companies of depriving them of the wealth produced on their land, has escalated in recent months into guerrilla warfare, with armed groups seeking to take control of the oil resources by force.

Movement for the Empancipation of Niger Delta (MEND) accuses President Obasanjo of continuing oppression by successive governments, leaving the region among Nigeria's poorest despite its oil wealth, and wants all foreign oil companies in the delta to leave.

"Expatriates must realise that they have been caught up in a war and the Nigerian government can do nothing to guarantee the security of anyone," the group said in its statement. "They are warned again to leave while the doors are still open."