Deep in the Algerian desert, special forces lay in wait, encircling a vast gas facility where dozens of foreign workers and hundreds of Algerians had been held captive for more than 24 hours.
The Islamist militant hostage-takers were feared to have booby-trapped the complex by placing mines along its perimeter or making its captives wear belts carrying explosives.
The military-dominated Algerian regime, still in the shadow of its own brutal 10-year civil war and now faced with a return to major operations on its home-turf, had a difficult choice: storm the facility and risk casualties, or wait it out as the crisis intensified. Algiers refused to negotiate with what it termed the "terrorists".
By midday, the Algerian special forces had launched a military operation at the site which was continuing into the night on Thursday. The regime said there had been deaths among the hostages, while Algerian sources told Reuters that 25 foreign hostages had escaped and six had been killed. However, the tone of statements from London and Washington led to fears that casualty numbers could rise dramatically. Algeria's official news service said 600 local Algerian workers had been freed. Dublin confirmed that a 36-year-old Irish worker, Stephen McFaul, from west Belfast, was unhurt.
It was unclear how the rescue offensive began. Islamists with the Masked Brigade inside the facility, who had been speaking by phone through a Mauritanian news outlet, said the Algerians opened fire as some militants tried to leave the vast Ain Amenas complex with their hostages. They claimed that 35 hostages and 15 militants died and seven hostages survived when Algerian helicopters targeted their convoy – an assertion that could not immediately be verified.
The Mauritanian news agency that was in communication with the hostage-takers – who had made demands including calls for French troops to leave Mali and for the release of Islamists in Algerian jails – said communications had gone down at about 5pm.
Abdelkader, 53, an Algerian employed at the facility who escaped, said the militants had indicated they would not harm Muslims but would kill western hostages they called "Christians and infidels". He said they appeared to have a good inside knowledge of the layout of the complex and used the language of radical Islam.
"The terrorists told us at the very start that they would not hurt Muslims but were only interested in the Christians and infidels," Abdelkader, 53, told Reuters from his home in the nearby town of In Amenas. "We will kill them, they said." "I am still choked, and stressed." He said he feared that many of his foreign colleagues may have died. "The terrorists seemed to know the base very well, moving around, showing that they knew where they were going."
Another Algerian who escaped told a French TV channel by telephone that the militants were "well dressed", spoke Arabic and appeared to be from north Africa or the Maghreb. It was the biggest and most dramatic foreign hostage-taking raid seen in Algeria or the Sahel, where the lawless desert has long been notorious for kidnap raids. It was also a meticulous and unprecedented strike at Algeria's economic heart; the southern energy complexes, never before hit by a terrorist raid, are the lifeblood of the oil- and gas-rich state, which exports large quantities to the US and Europe.
The jihadists who lay in wait outside the Ain Amenas gas field in the early hours of Wednesday morning were either very lucky with their timing or extremely well informed.
About 20 of the militants had arrived on three pickup trucks at a time when there appears to have been more than double the usual number of foreign contractors at the remote desert site. They struck at 5am, just as the gates of the living quarters were swung open and a bus emerged, taking a group of westerners to the Ain Amenas airport about 20 miles away.
The convoluted metal tubes, glowing eerily under bright night lights in a vast expanse of flat featureless desert, give the gas field in the settlement at Tigantourine the look of an outpost on an alien planet, and it is scarcely more hospitable. The workers stayed in their barracks under police guard, leaving only to travel the two miles of tar road between their trailers and tents and the gas pumping station.
The gas field, run by the Algerian state firm, Sonatrach, BP and Norway's Statoil, produces 9bn cubic metres of natural gas a year, one-tenth of Algeria's total production, representing a mainstay of the nation's income. It was proud boast of the government in Algiers that through all the turbulence of recent decades, in which the Sahel has become a cauldron of political and religious extremism, the state had protected its oil and gas installations. No one had been allowed to get near them, until Wednesday morning.
The attackers first opened fire on the bus carrying foreign workers, but its escort of police and private security guards fought back. One British worker was killed in the exchange along with an Algerian guard, the government said.
Two Britons, a Norwegian and three other guards were injured, but the bus escaped and sped across the desert, taking the wounded to the hospital in Ain Amenas, a small border town of 5,000 people.
In Tigantourine, the attackers turned their focus on the workers' camp, storming in from two directions, according to one hostage who gave an account to French television. In an operation that had all the signs of being planned well in advance, they rounded up their hostages, isolating foreigners from Algerians, lay down explosives and called the press.
One worker originally from France told a journalist from France 24 TV station: "They attacked both sites at the same time. They came inside and, as soon as it was light, they rounded everybody up."
He said he was with British, Japanese, Filipinos and Malaysians and that the attackers, who were heavily armed, had made some hostages wear belts of explosives. It was not possible to verify whether his testimony was made under duress.
There were at least 150 Algerian workers present on the site employed by the French catering group CIS. One Algerian worker who spoke to the Maghreb Emergent website by phone said: "There are around 300 of us. It's the foreigners that interest them."
Some hostages managed to contact their families. A Norwegian woman told the Bergens Tidende newspaper that her husband, 55, had called her saying he had been taken hostage.
A spokesman for the militants, said to have spoken by phone from the gas complex with the Mauritanian news agency, threatened to "eliminate" the hostages if Algerian forces attacked.
Early in the siege, one hostage, identified as British, was quoted as calling for negotiations to "spare any loss of life". He said: "We are receiving care and good treatment from the kidnappers. The [Algerian] army did not withdraw and they are firing at the camp."
More than 24 hours after the hostage siege began, BP, which considers itself the largest foreign investor in Algeria, said it was evacuating workers from other hydrocarbon sites. French energy groups were reported to be doing the same.
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