The final onslaught of Algerian special forces on a gas installation where foreigners were being held by Islamist militants killed 11 kidnapers and seven hostages, the state news agency reported.
Algerian Press Service says the troops stormed the facility on Saturday after a four-day standoff in which militants occupied the Ain Amenas natural gas facility in southern Algeria.
Al Arabiya reporter from Algiers said two Americans, one Japanese and one Norwegian were among those killed on Saturday.
The heavily armed gunmen from a group known as "Signatories in Blood" had been holed up in the In Amenas gas complex since they took up to 41 foreign worker hostage in a dawn assault on Wednesday.
"The (army) assault took place mid-morning. Eleven terrorists lost their lives along with the foreign hostages," the security source told AFP.
"We think they were killed in retaliation" for the army attack, the source said.
"Signatories in Blood," led by Algerian Mokhtar Belmokhtar, a former senior Al-Qaeda commander in north Africa, were demanding an end to French intervention against Islamists in neighboring Mali, ANI reported earlier.
Belmokhtar also wanted to exchanging American hostages for the blind Egyptian sheikh Omar Abdul Rahman and Pakistani Aafia Siddiqui, jailed in the United States on charges of terrorist links.
The plant is jointly run by BP, Norway's Statoil and Algeria's state-owned oil company.
An international outcry mounted over the Algerians' handling of the crisis. Experts noted that this is how they have always dealt with terrorists, refusing to negotiate.
The standoff has put the spotlight on militancy plaguing the region and al-Qaida-linked groups roaming remote areas from Mali to Libya, threatening vital infrastructure and energy interests.
The militants attacked the plant Wednesday morning, creeping across the border from Libya, 60 miles (100 kilometers) from the natural gas plant, and fell on a pair of buses taking foreign workers to the airport. The buses' military escort drove off the attackers in a blaze of gunfire that sent bullets zinging over the heads of the crouching workers. A Briton and an Algerian, probably a security guard, were killed.
Frustrated, the militants turned to the vast gas complex, divided between the workers' living quarters and the refinery itself, and seized hostages, the Algerian government said. The gas flowing to the site was cut off, though the circumstances of the cutoff remain unclear.