The militants had filled five jeeps with hostages and begun to move when Algerian government attack helicopters opened up on them, leaving four in smoking ruins. The fifth vehicle crashed, allowing an Irish hostage inside to clamber out to safety with an explosive belt still strapped around his neck.

Three days into the crisis at a natural gas plant deep in the Sahara, it remained unclear how many had perished in the faceoff between Africa's most uncompromising militant group and the region's most ruthless military.

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By Friday, around 100 of the 135 foreign workers on the site had been freed and 18 of an estimated 30 kidnappers had been slain, according to the Algerian government, still leaving a major hostage situation centered on the plant's main refinery.

The government said 12 workers, both foreign and Algerian, were confirmed dead. But the extremists have put the number at 35. And the government attack Thursday on the convoy — as pieced together from official, witness and news media accounts —suggested the death toll could go higher. The U.S. government confirmed that one of the dead was a Texan, Frederick Buttaccio.

Meanwhile, the al-Qaida-linked Masked Brigade behind the operation offered to trade two American hostages for two terrorists behind bars in the U.S., including the mastermind of the 1993 World Trade Center bombing — a deal the U.S. rejected out of hand.

The remote In Amenas plant, jointly run by BP, Norway's Statoil and Algeria's state-owned oil company, is deep in the featureless desert. The Algerian government has released few details about the continuing siege.

By Friday, however, the outlines of the takeover by Islamic militants were coming into focus. The attack had been in the works for two months, a member of the Masked Brigade told an online Mauritanian news outlet that often carries al-Qaida-related announcements. The band of attackers included militants from Algeria, Mali, Egypt, Niger, Mauritania and Canada, he said.

He said militants targeted Algeria because they expected the country to support the international effort to root out extremists in neighboring Mali.

Instead of passing through Algeria's relatively well-patrolled deserts, the attackers came in from southern Libya, where there is little central government and smugglers have long reigned supreme, according to Algeria's Interior Minister Daho Ould Kabila.

He said the attackers consisted of about 30 men armed with rocket launchers and machine guns and under the direct supervision of the Masked Brigade's founder himself, Moktar Belmoktar, a hardened, one-eyed Algerian militant who has battled the Algerian government for years and went on to build a Saharan smuggling and kidnapping empire linked to al-Qaida.

Early Wednesday morning, they crept across the border, 60 miles 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.

One American killed, 2 escape in hostage crisis, U.S. officials say; two others reportedly still held

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 takeover soon turned into a standoff as military units from a nearby base surrounded the complex.

Algerians interviewed by French radio described militants knocking down doors in the living quarters, saying they were looking for foreigners. The foreign workers, including Americans, Britons, French, Norwegians, Romanians, Malaysians and Japanese, were separated from the Algerians and kept under close guard, wrapped with explosive belts. The Algerians for the most part were allowed to wander freely around the complex, and some were released, according to the state news agency.

Alexandre Berceaux, a Frenchman who was later rescued by Algerian soldiers, described two harrowing days of confusion hiding in his room as Algerian colleagues supplied him with food.

"I stayed hidden in my room for almost 40 hours," he told Europe 1 radio, saying he hid under the bed and didn't even realize when his ordeal was over.

The militants declared that the takeover was prompted by France's attacks on al-Qaida-linked rebels in Mali, and they demanded that the intervention end or the hostages would pay for it.

That night, Kabila, Algeria's top security official, announced that in accordance to Algeria's longstanding policy, "we reject all negotiations with the group." Despite regular elections, Algeria is run by a coterie of generals and ruling party leaders who got the country through a bloody, decade-long Islamist rebellion with brutal tactics that earned them the nickname "the eradicators."

On Thursday afternoon, Algerian military forces saw a five- jeep convoy moving from one part of the complex to another. Fearing the kidnappers were trying to make a break for it, they sent attack helicopters into action.

Irish electrician Stephen McFaul was in that convoy and made it out alive as the world exploded around him.

"Four of the jeeps were taken out and everybody in them was killed," McFaul's brother, Brian, told the Irish Times. "The jeep my brother was in crashed and my brother made break for it," with a belt of explosives strapped around his neck.

The kidnappers called the Mauritanian news service ANI to say that 35 hostages and 15 of their fighters had been killed in the bloodbath — a figure that was impossible to confirm. The kidnappers told ANI that they were just trying to consolidate hostages into a single location when the Algerians attacked.

By Thursday night, the state news agency announced that the assault was over and that special forces had secured the plant, but the next day it would emerge that they had taken only the living quarters. The hostages and their kidnappers remained ensconced in the refinery.

An international outcry mounted over the Algerians' handling of the crisis. Experts noted that this is how they have always dealt with terrorists.

"It's the Russian training for dealing with terrorism," said Matieu Guidere, a longtime expert on al-Qaida and Algeria. "The message is: We will terrorize the terrorists. ... This is clear. The life of hostages is nothing in the balance."

The Algerian government insisted it had to intervene to prevent a catastrophe.

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