LAGOS: Nigeria's military on Wednesday 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 oil 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.

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 an attack on an oil rig and support vessel.

The remaining four were believed taken in another incident in the region, the sources said.

There was no immediate indication of whether ransoms were paid for any of the hostages.

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.

The military and police joint task force “is at the moment engaging in a mop-up operation to look for criminals and those making life and property unsafe in the Niger Delta,” spokesman Lieutenant Colonel Timothy Antigha had said.

Antigha 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 in recent months had seen a new round of attacks. Many observers say the amnesty has failed to address underlying issues of poverty and unemployment in the Niger Delta.

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.