A militant group has claimed responsibility for killing four police officers this week and says it is in contact with the kidnappers of three foreign crew members.
The Movement for the Emancipation of the Niger Delta claimed Thursday's attack on police in an email to journalists Friday.
Police said the four police officers were on a boat patrolling the Nembe river in Bayelsa state when gunmen shot them.
The group's statement also said the kidnappers of three foreign crew members have offered to hand over their hostages to the group. It said the hostages were in good health.
The International Maritime Bureau had reported that a captain and chief engineer were kidnapped off a vessel anchored in the city of Port Harcourt during an attack by pirates Tuesday. It said a crew member was also missing.