Nigerian militants have claimed responsibility for exploding a car bomb at an army barracks in the southern oil city of Port Harcourt.
Two people died in the attack a day after the Movement for the Emancipation of the Niger Delta renewed its threat to target oil installations.
On Wednesday, Mend rejected plans announced by President Olusegun Obasanjo to develop the Niger Delta.
The militants are demanding more local control of the region's oil wealth.
In recent months there has been an upsurge of attacks on foreign oil interests which have cut the country's oil production by 20%.
This has cost Nigeria millions of dollars of lost revenue and helped to drive up world oil prices.
Warning
In a statement, Mend said the attack which killed two people and critically injured six more on Wednesday night "was symbolic rather than strategic".
The group said the attack was a warning to the Nigerian military and the oil companies in the area and proved that the Nigerian military was incapable of protecting itself, let alone protecting the oil industry.
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