One of seven foreign oil workers taken hostage Wednesday was killed and another was wounded during a rescue attempt that also left two kidnappers and a soldier dead, according to Nigerian and private security officials.

Gunmen had seized the seven hostages from an Italian oil supply vessel off the coast of southern Nigeriain the latest attack by militants on facilities in the volatile Niger Delta, where most of the country's oil is produced.

Government and private security officials who spoke on condition of anonymity because they were not authorized to talk to the media said the four were killed during the rescue attempt.

In all, 25 foreign workers and nearly 60 Nigerian employees had been aboard the vessel belonging to a subsidiary of Italian oil giant Eni SpA that was attacked overnight, Eni said.

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The company said 10 armed men attacked the ship and took the hostages away on a speedboat, grabbing two Finnish citizens along with an Italian, a Filipino, a Briton, a Pole and a Romanian.

A private security contractor said that nearly all those on the vessel were held at gunpoint for a period before the attackers left with the seven captives.

Most oil workers kidnapped in the past year have been safely released. The captives are usually freed after a ransom is paid by the companies and the government, according to security analysts.

Since the beginning of 2006, militant groups have attacked pipelines and taken workers hostage in violence that has cut about 25 percent of Nigeria's usual crude output of about 2.5 million barrels daily. Civilian protesters have also taken over oil facilities to protest lack of jobs and development.

On Monday, Eni said a two-week armed siege at its Tebidada oil pumping station in Nigeria ended peacefully and the company resumed an output of 50,000 barrels per day. The facility, located in Bayelsa state, had been occupied Nov. 6 by a group of militants and villagers who took 48 Nigerian staff members hostage, seeking compensation from the company for oil spills. Several hostages escaped and some were released.

Despite Nigeria's being Africa's biggest oil producer, most inhabitants of the oil-rich delta remain poor. The country is the world's eighth-biggest oil exporter and the fifth-largest source of U.S. oil imports.

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