Nigerian militants released pictures of seven foreign oil worker hostages on Thursday, showing the men sitting on a bench with guns pointed at their heads.
The pictures, taken in what appeared to be a jungle setting, were sent to Reuters from an email address which has previously been used by the militants.
The militants seized nine men, including the seven in the pictures, from a barge run by U.S. oil services company Willbros last Saturday.
The photographs were accompanied by a message reading: “Pictures of our guests along with a part of the unit that captured them.”
The militants have threatened to seize more Westerners from towns in the southern Niger Delta and warned of more attacks on Nigeria’s oil industry.
Attacks by the Movement for the Emancipation of the Niger Delta have already cut Nigerian oil exports by a fifth. Nigeria is the world’s eighth-largest oil exporter.
The militants have demanded the release of two ethnic Ijaw leaders and more local control over the region’s huge oil wealth. The Ijaw are the dominant tribe in the delta.