The crew members seized near Bonny in southern Rivers State on Friday have not been identified, but the military believe they are from eastern Europe.

“Gunmen attacked the cargo vessel BBC Palonia and one other four nautical miles south of Bonny River,” said navy spokesman Lt. Edward Yeibo. “The gunmen shot one dead and took others hostage.”

Military officials were in contact with the kidnappers, demanding the immediate release of the hostages, said a navy commander in the capital Abuja.

Commodore David Nabaida told The Associated Press that pirates boarded the German-flagged cargo ship BBC Palonia Friday night off the coast of the Niger Delta. A struggle broke out during the attack and pirates shot one crew member in the leg during the fight, Nabaida said.

“All efforts are being made to ... rescue the kidnapped crew,” the commodore said.

Nabaida said the navy had suspects in mind for the attack, but declined to offer further details. He did not know the nationality of those taken during the attack.

Militants have kidnapped oil workers, bombed crude pipelines and fought with government troops since an insurrection began in the Niger Delta in 2006. While a government-sponsored amnesty deal has slowed violence in recent months, analysts worry the program has begun to fray as weapons remain plentiful in the impoverished region.

Saturday’s attack comes as acts of piracy increase in the Gulf of Guinea, especially along Nigeria’s 530 miles of coastline.

Africa’s most populous country remains a target-rich environment full of oil barges and oil company ships near the delta, one of the US’ top sources of crude oil. Cargo ships off the coast of the megacity of Lagos also fall under pirate attacks as they wait to unload their goods at the city’s busy and mismanaged ports.

The International Maritime Bureau, which tracks piracy worldwide, reported 28 attacks off Nigeria during 2009. The bureau also believes at least another 30 pirate attacks went unreported, either due to companies worrying about having higher insurance premiums or concerns about advertising their security weaknesses.