CBS/AP/ January 21, 2013, 2:32 PM

Algeria: Canadians among Islamist hostage-takers

In this undated photo, men look at the wreckage of a vehicle near Ain Amenas, Algeria, where Islamist militants stormed a gas plant, taking dozens of workers hostage. / AP Photo/Echorouk Elyaoumi

Last Updated 2:32 p.m. ET

ALGIERS, Algeria

The Islamist militants who attacked a natural gas plant in the Sahara included two Canadians and a team of explosives experts who had memorized the layout of the sprawling complex and were ready to blow the place sky-high, Algeria's prime minister said Monday.

Militants in the highly-organized operation also wore Algerian army uniforms and appeared to have help from the inside — a man from Niger who had once worked as driver at the plant, he said.

Algeria detailed a grim toll from the attack, saying that 38 hostages and 29 militants died in four days of mayhem. Three of the attackers were captured and five foreign workers remained unaccounted for, Prime Minister Abdelmalek Sellal told reporters at a news conference in Algiers, the capital.

He did not specify the nationalities of the captured militants, report their medical conditions or say where they were being held.

Monday's account offered the first Algerian government narrative of the four-day standoff, from the attempted bus hijacking early Wednesday to the moment when the attackers prepared to explode bombs across the gas plant, which spreads out over 2 square miles deep in the desert, 800 miles south of Algiers.

All but one of the dead hostages — an Algerian driver — were foreigners. The dead hostages included seven Japanese workers, six Filipinos, three energy workers each from the U.S. and Britain, two from Romania and one worker from France.

The final death toll was still unclear, since accounts from other governments appeared to indicate that more than five workers were still missing. It was also lower than the 81 estimated Sunday from Algerian reports of dead and missing.

The militants had said during the standoff that their group included Canadians, and hostages who had escaped recalled hearing at least one of the militants speaking English with a North American accent.

In addition to the Canadians, the Algerian prime minister said the militant cell included men from Egypt, Mali, Niger, Mauritania and Tunisia, as well as three Algerians.

Officials in Canada could not immediately confirm whether two of the attackers were citizens.

"Canada condemns in the strongest possible terms this deplorable and cowardly act and all terrorist groups which seek to create and perpetuate insecurity," said Chrystiane Roy, a spokeswoman for the Department of Foreign Affairs.

"We are pursuing all appropriate channels to seek further information and are in close contact with Algerian authorities," she said in a statement.

The Algerian prime minister indicated that this operation was not — as the Islamists had claimed — an immediate reaction to France's recent military intervention against Islamists in neighboring Mali, since the captured militants said it took two months of planning. But he said the group did come from northern Mali, hundreds of miles away from the gas plant.

He said they included a former driver at the complex from Niger and "knew the facility's layout by heart." They wore Algerian military uniforms, he said, bolstering accounts by escaped hostages that they didn't just shoot their way in.

"Four attackers stepped out of a car that had flashing lights on top of it," one of the former hostages, Liviu Floria, a 45-year-old mechanic from Romania, told The Associated Press.

The prime minister said "the last words of the terrorist chief" was to slaughter the hostages.

"He gave the order for all the foreigners to be killed, so there was a mass execution, many hostages were killed by a bullet to the head," he said.

Play Video

Algerian hostage crisis: Death toll now more than 80

CBS News correspondent Mark Phillips says that while the French intervention in Mali has been given as the motivation for the attack, the equipment, the uniforms, the fact the Algerians say the kidnappers had maps of the facility and possibly had planted some people on the inside as employees are all signs the Islamist militants in North Africa had planned the attack for some time -- and that this attack will not be the last.

Algeria's tough and uncompromising response to the crisis was typical of its take-no-prisoners approach in confronting terrorists, favoring military action over negotiation. Algerian military forces, backed by attack helicopters, launched two assaults on the plant, the first one on Thursday.

The militants had "decided to succeed in the operation as planned, to blow up the gas complex and kill all the hostages," Algerian Communications Minister Mohamed Said told state radio.

Three Americans died in the attack and seven made it out safely, a U.S. official in Washington said, speaking on condition of anonymity because he was not authorized to speak publicly. Their bodies have been recovered, the official said.

Official: 3 Americans total died in Algeria attack

Algeria has not reported any military deaths from four days of confronting the fighters.

The attack began early Wednesday with the attempted hijacking of two buses filled with workers outside the complex. Under assault from Algerian forces, the militants moved on the main complex, armed with missiles, mortars and bombs for their three explosives experts, Sellal said.