A French oil firm says gunmen attacked a boat off the coast Cameroon, killing five people, including three Cameroonian guards for Perenco's offshore oil field.
The Associated Press has identified the other two victims in the attack late Tuesday night as civilian security contractors working for Perenco.
This is the second incident reported this week involving oil rigs and their crews in the region.
Nigeria's main militant group has claimed responsibility for Monday's attack on an Exxon Mobil oil platform off the coast of southern Nigeria.
In a statement Tuesday, the Movement for the Emancipation of the Niger Delta (MEND) has said it kidnapped seven local workers in the raid and threatened future attacks.
Exxon said Monday gunmen had attacked the rig off Nigeria's Akwa Ibom state, but gave no further details.
In a similar raid on November 7, gunmen abducted seven people from an oil rig in the same area in an attack that also wounded two others.
The region is home to criminal gangs that have a history of taking hostages for ransom. Militants say they are fighting for more equitable distribution of oil revenue.