Jomo Gbomo, a spokesman for the Movement for the Emancipation of the Niger Delta, known as MEND, sent a statement to Next.com saying MEND planned to release the names of the hostages within the next 24 hours, Timbuktu Media reported.
MEND took over the oil rig run by Transocean off the southern coast of Nigeria Sunday, injuring two of the crew members.
A spokesman for the rig's owner, London-based Afren PLC, said the injured workers had been shot in the legs and were reported in stable condition after being airlifted to a shore-based clinic.
The spokesman told CNN the attackers were holding two Indonesians, two Americans, two French citizens and one Canadian.
U.S. State Department spokesman P.J. Crowley said the United States is in contact with Nigerian officials.