Those freed included two Americans, two Frenchmen, two Indonesians and a Canadian taken from an Afren oil rig, eight Nigerians abducted from an Exxon Mobil platform and four others, two sources involved in the operation said.
“It was a land, air and marine assault. They have all been freed, all 19 of them,” one of the sources said.
The military taskforce , said earlier it was carrying out several operations simultaneously across the Niger Delta but gave no details.
A military spokesman declined to comment further on the operation or confirm whether the hostages had been freed, saying a statement would be issued on Thursday.
There was no immediate comment from the companies whose employees were abducted.
France’s Foreign Minister confirmed two of its nationals had been released: “This happy ending does not make us forget the fate of the other French nationals still held hostage, for which the government is as mobilised as ever,” French Foreign Minister Michele Alliot-Marie said, refering to French nationals held elsewhere.
France now has eight nationals held overseas including five in Mali, two in Afghanistan and one in Somalia.
A second security source involved in planning the operation said former militant leaders who accepted the amnesty brokered by President Goodluck Jonathan last year had been instrumental in securing the safe release of the kidnapped oil workers.
“There was a strong element of co-operation between the former militant leadership and the security forces in the release of the 19 hostages,” the security source said.
“What happened today in Nigeria has never happened before. It shows the strength not only of the security forces but of the former militant leadership and the amnesty programme,” the source said, also asking not to be named.
The release of the hostages appears to mark a key victory for the authorities in the Niger Delta at a time when militants, who have in the past caused major disruption to the OPEC member’s mainstay industry, have been staging a comeback.
Previous campaigns by militant fighters have knocked out a significant chunk of Nigeria’s oil production, currently averaging about 2.2 million barrels per day (bpd), and cost it as much as $1 billion a month in lost revenues.
The Movement for the Emancipation of the Niger Delta (MEND), the main militant group in the region, claimed responsibility for the attacks on Afren and Exxon and has warned of further strikes against energy industry facilities.
It had also warned the security forces against any operation to free the hostages, saying it would endanger their lives.
Those held included eight Nigerians taken on Sunday from a platform operated by U.S. firm Exxon Mobil.
Of the seven hostages taken from the Afren rig a week earlier, the two Americans and one of the Frenchmen were employees of Swiss-based Transocean. A second Frenchman worked for France’s Sodexo, the Indonesians worked for Century Energy Ltd and the Canadian worked for local firm Petroleum Projects International (PPI), according to MEND.
Several MEND field commanders agreed to lay down their weapons last year and the government says thousands of their gang members followed suit, in return for a presidential pardon, stipends, and the promise of re-training.
Henry Okah, believed to be one of the masterminds behind MEND, has been detained in South Africa in connection with car bomb attacks in the Nigerian capital Abuja on October 1 which killed at least 10 people and were claimed by the group.