A dozen foreign seafarers seized two days ago in Nigeria's restive and oil rich Niger Delta were freed on Sunday, military officials said.
"I can confirm to you they have indeed been released. They are on their way to Bonny (main oil terminal in the Niger Delta) where their ship is anchored," Lieutenant Colonel Timothy Antigha, spokesman for a special security force deployed in the area, said.
No-one claimed responsibility for the capture of the BBC Polonia, registered in the Caribbean nation of Antigua and Barbuda, and its multinational crew, including its 71-year-old German captain.
The main armed group, the Movement for the Emancipation of the Niger Delta (MEND) said it was "not involved in this attack but we are aware of the group that carried out the abduction".
Security officials said they were in the dark as to who was behind the attack and abduction.
Navy spokesman, David Nabaida said the men were dropped off in a fishing trawler and the navy went to collect them.
"Our boats have gone to receive them from the fishing trawler. I don't know who is behind them, but I think it's one of the factions of the ex-militants," he said.
Germans and Russians were among the 12 seafarers captured in Friday's incident, during which a Ukrainian seaman was reportedly injured.
Hundreds of locals and foreigners have been abducted in the Niger Delta in recent years, against the backdrop of conflict in the oil-producing region where a government amnesty has failed to totally eliminate militancy.