Thirty-seven foreign hostages of eight nationalities were killed in the siege at a BP desert gas plant in Algeria, the Algerian prime minister said.
In a Monday press conference, Abdelmalek Sellal said that five foreigners remained missing, and seven bodies remain unidentified.
Some were found shot in the head at close range, the prime minister said, according to the BBC.
Later on Monday, the US State Department named three Americans killed in the attack. The three gas workers were identified as Victor Lynn Lovelady, Gordon Lee Rowan and Frederick Buttaccio, USA Today reported. Spokeswoman Victoria Nuland said seven Americans had survived the attack but would not name them.
France 24 said the others killed included seven Japanese, six Filipinos, three Britons, two Romanians, at least one Canadian, and one Frenchman. At least one Algerian captive was also killed.
BP announced Monday it could not account some of its employees' whereabouts. Chief Executive Bob Dudley said in a statement:
"As the situation continually changes, we are doing all we can to locate them, working with the relevant British and Algerian government authorities and agencies. While not confirmed, tragically, we have grave fears that we are likely to have suffered one or more fatalities."
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Meanwhile, 29 hostage-takers died in the Algerian army's four-day siege on the complex at In Amenas, in eastern Algeria. Three were captured alive, Sellal said.
Sellal said the jihadists had crossed into the country by way of neighboring Libya, according to Reuters, which also cited an Algerian newspaper reporting the terrorists had arrived in cars registered in Libya.
Sellal said the hostage-takers came from seven different countries: Mali, Algeria, Tunisia, Niger, Mauritania, Egypt and Canada. A Canadian national was "coordinating the attack," the prime minister said.
Earlier, an Algerian security source told Reuters that two of the hostage-takers found dead had been identified as Canadian. Asked by Canada's Globe and Mail, the Canadian Foreign Affairs Ministry said simply that it was in contact with Algeria and awaiting further information.
Sellal said that the militants had originally planned to kidnap a bus full of plant employees and take them into Mali, but they were prevented by armed guards protecting the vehicle.
According to the premier, Algerian troops intervened when it became evident that the hostage-takers intended to "blow up" the In Amenas complex.
The suspected mastermind of the attack is veteran jihadist Mokhtar Belmokhtar, a former commander with Al Qaeda in the Islamic Maghreb (AQMI).
In a statement issued to Mauritania's ANI news agency on Monday, the group that Belmokhtar now leads, the Mulathameen Brigade, threatened to carry out further attacks against any country involved in the fight against Islamist insurgents in Mali.
"We in Al Qaeda announce this blessed operation," he said.
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