Seven oil workers kidnapped from an offshore oil field in the Niger Delta were freed.
The workers - three foreigners and four Nigerians - were seized Saturday night after gunmen in more than 30 speedboats attacked EA field, operated by Royal Dutch Shell. It was the first major attack since the president began a peace process in the region five months ago.
"Yes, they have been released," Bayelsa state police spokesman Inyebom Inidong told The Associated Press. He had no further details.
The foreign hostages are British, Croatian and South African. Shell originally reported that the South African was Russian.
The Niger Delta has been the scene of frequent disputes between oil companies and communities who have for years demanded a greater share of the wealth of Africa's largest crude producer. The region remains desperately poor despite its great natural bounty.
Around 100 foreign workers have been kidnapped since the beginning of the year.
The government of President Umaru Yar'Adua has stepped up efforts to calm the oil-producing region, and violence has waned since he took power May 29. But the latest attacks could set back plans for Yar'Adua to hold formal talks with the main armed groups.
One prominent militant group, the Movement for the Emancipation of the Niger Delta, has refused to confirm or deny reports that it was behind the attack.
The EA field has been closed since February 2006 because of an earlier militant attack, but it had been due to resume operations by the middle of next year.
The head of the Voronezh region, Alexander Gusev, confirmed the death of Major General Vladimir Zavadsky.