Nigeria's military freed 19 hostages in an operation in the country's main oil-producing region, including Nigerians and foreigners, two security sources said.
"We've got confirmed reports that, yes, all 19 have been reported freed," one of the security sources said.
"It was a JTF operation," he added, referring to Nigeria's Joint Task Force, which includes police and military personnel.
Another security source also said they had been released. Those released included two French, two Americans, two Indonesians, a Canadian and Nigerians, the sources said.
The victims were all taken hostage in recent raids on facilities in the country's Niger Delta region, the heart of one of the world's largest oil industries.
France's foreign minister had earlier confirmed that the two French nationals were freed.
"Michele Alliot-Marie is pleased with the release of the two Frenchmen who had been taken hostage, along with five other people, on an oil platform in Nigeria overnight November 7-8," a statement said.
Canada's Foreign Minister Lawrence Cannon also welcomed the news Wednesday.
"We would like to thank everyone who worked to ensure a safe and peaceful resolution to this incident," Cannon said.
Nigeria's main militant group MEND had claimed responsibility for kidnapping 14 of the hostages. Those released were believed taken in three separate incidents.
A spokesman for a joint military and police force in the Niger Delta declined to provide details, saying only that an operation had been underway and a briefing would be held on Thursday.
The military had at the weekend warned of action in the Niger Delta and urged residents living near militant camps to clear out.
Eight of the hostages were believed taken in an attack this week on an ExxonMobil facility, while seven others were kidnapped last week in a raid on a support vessel and Transocean oil rig overseen by Afren.
The remaining four were believed to be employees for Julius Berger taken in another incident, the sources said.
There was no immediate indication of whether ransoms were paid for any of the hostages.
Last week, three French workers for maritime services firm Bourbon seized from an oil industry supply vessel in September were also freed.
They were kidnapped when armed pirates in several speedboats attacked their 2,000-tonne vessel off Nigeria.
MEND -- the Movement for the Emancipation of the Niger Delta -- has claimed scores of attacks in the Niger Delta.
In a statement on Tuesday, it warned of a "major operation" and claimed one of its camps had come under military fire on Monday.
Nigerian authorities had at the time confirmed operations were underway to hunt down kidnappers, but provided few details.
Lieutenant Colonel Timothy Antigha had said the operation would continue "until the desired level of security and peace is achieved in the Niger Delta and the region is rid of criminal and illegal actions by the so-called militants."
Unrest in the Niger Delta, before the government offered an amnesty deal to militants last year, had slashed production in one of the world's largest oil exporters.
The amnesty was credited with greatly reducing unrest in the region and oil production has rebounded to an estimated 2.2 million barrels per day, but there has been a new round of attacks in recent months.
Many observers say the amnesty has failed to address underlying issues of poverty and unemployment in the Niger Delta. Militant leaders given stipends in exchange for turning in their weapons would eventually be replaced by others, they warned.
MEND, which claims to be fighting for a fairer distribution of oil revenue, has also been seen as an umbrella organisation for criminal gangs. It is believed to have splintered, particularly over the amnesty.
The recent attacks come ahead of elections set for early next year. President Goodluck Jonathan, who is running in the elections, is from the Niger Delta and faces pressure to resolve the situation in the region
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