Nigerian militant group MEND said all the hostages taken from an Italian-operated offshore oilfield earlier on Thursday had been released.
The self-styled leader of the Movement for the Emancipation of the Niger Delta (MEND) said his group had not intended to take more hostages, having seized six foreign workers from a U.S.-operated oilfield on Tuesday.
"They have all been released within the last five minutes and are on their way to Port Harcourt," said the leader, who uses the pseudonym Jomo Gbomo.
Gbomo said eight people were taken from the Mystras oil production vessel, operated by Saipem and SBM Offshore, which normally produces about 50,000 barrels per day of crude oil.
Saipem's parent company Eni put the number of abducted at six, including one British, one Australian, one Polish, two Croats and one Romanian.
MEND, which says it is fighting for more regional control of the delta's oil wealth, has said the six hostages taken on Tuesday from a Chevron oilfield would be released unconditionally on May 30.