Armed men attacked the offices of a Nigerian aid group in the southern oil hub of Port Harcourt, killing one person and wounding another, the organization's head said Monday.

Judith Asuni of Academic Associated Peaceworks said that the dead man had offered to help find Ateke Tom, a militant wanted by the Nigerian government in connection with a string of kidnappings and bank robberies.

Click here to go to FOXNews.com's Africa Center.

Asuni's group promotes conflict management and peace education in Nigeria and Ghana, and has spent recent years focusing on Nigeria's restive oil delta.

Meanwhile Italian energy giant Eni SpA said a two-week armed siege at a crude oil pumping station it operates ended late Sunday, with all hostages released unharmed.

Eni said it intended to resume production soon at the Tebidada flow station, operated through Eni's subsidiary Agip. The facility has an output of 50,000 barrels a day.

The facility, located in Bayelsa state, was 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. Thirty-five had remained in captivity.

"All personnel is in good health, and production will be restored shortly once the necessary checks have been completed," Eni said. A spokeswoman said she did not immediately know if any damage occurred in the takeover.

Hafiz Ringim, Bayelsa state police commissioner in charge of the area, said he had no information on the hostage release and could neither confirm nor deny it.

Eni's equity stake in oil output from the facility is about 9,000 barrels a day. Most of the rest is held by Nigeria's state-run company.

The takeover was the latest in a series of attacks on oil installations in the volatile Niger Delta, where most of Nigeria's oil is produced.

Since the beginning of this year, militant groups have attacked oil pipelines and taken oil workers hostage in violence that has cut about 25 percent of the country'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 in the regions.

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

Despite Nigeria being Africa's biggest oil producer, most inhabitants of the oil-rich delta remain poor.

Nigeria is the world's eighth-biggest oil exporter and fifth-largest source of U.S. oil imports.