AIN AMENAS, Algeria - Algerian security forces tried Saturday to bring an end to a four-day-old standoff with Islamist extremists holding foreign hostages at a remote gas plant, a drama that has left at least 12 dead and horrified governments around the world.

Algerian authorities gave no clear sign of how many people are still alive or captive at the Ain Amenas plant in southeast Algeria as of Saturday morning. The plant is jointly run by BP, Norway's Statoil and Algeria's state-owned oil company.

Casualty figures varied widely. The Algerian government says 12 hostages and 18 militants died in a military attack on a convoy of militants Thursday. The militants claimed that 35 hostages were killed, according to a Mauritanian website, ANI, that is close to the extremists.

One American, from Texas, is among the dead, and the militants offered to trade two American hostages for two terrorists behind bars in the U.S., an offer firmly rejected by Washington. Britons, French and Algerians have also died in the standoff.

Hundreds of Algerian and foreign workers have been freed, some describing being used as human shields and having explosives strapped around their necks after the militants burst into the plant on Wednesday.

Ruben Andrada, 49, a Filipino civil engineer who works as one of the project management staff for the Japanese company JGC Corp, described the bloody aftermath of Algerian helicopter gunship barrage on vehicles carrying hostages and the gunmen, which he narrowly escaped.

His wife, Hedelyn Andrada, said she received a text message from her husband Wednesday saying there was gunfire near their housing complex at the site. He later told her that he and about 35 others, including seven other Filipinos, were seized by gunmen and made to wear a "bomb necklace."

On Thursday, all the hostages, about 35, were loaded into seven SUVs in a convoy that included 15 militants from the housing complex and used as human shields. He said they were being moved to the gas plant itself when the convoy was chased by army helicopters that fired on the vehicles.

"When we left the compound, there was shooting all around. I closed my eyes. We were going around in the desert. To me, I left it all to fate. The gunman behind me was shooting at the gunship and it was very loud. Then we made a sudden left turn and our Land Cruiser fell on the right side where I was. I was pinned down by the guy next to me. I could hear the helicopter hovering above. I was just waiting for a bullet from the helicopter to hit me," Andrada told The Associated Press.

He later saw the blasted remains of other vehicles, and the severed leg of one of the gunmen. Another hostage who survived, an Irish man, reported seeing a severed head from one of the vehicles.

Andrada said their vehicle separated from the convoy and overturned, allowing him and the others inside to escape. He suffered cuts and bruises and was grazed by a bullet on his right elbow.

They were taken to the Alazhar hospital in Algiers. He said the others suffered more serious injuries and were in the intensive care unit. He said the Algerian defense minister came to visit him in the hospital and apologized.

Philippines Foreign Affairs Department spokesman Raul Hernandez said 34 Filipino workers have been evacuated from the gas field and flown to Spain for repatriation to the Philippines.

Andrada's chilling account matched that of an Irish hostage also in the truck that was spared the Algerian army's fire.

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 hostages to clamber out to safety.

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.

Statoil CEO Helge Lund said Saturday that two more Norwegian workers have escaped from the plant and are safe, leaving six more Norwegians unaccounted for. There were 17 Norwegians at the plant at the time of the attack.

The attack by the Mali-based Masked Brigade had been in the works for two months, a member of the brigade told the online Mauritanian news outlet. He said militants targeted Algeria because they expected the country to support the international effort to root out extremists in neighboring Mali.

Early Wednesday morning, they crept 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.

Several of the former hostages, who arrived haggard-looking on a late-night flight into Algiers on Friday, said that the gunfire began around 5 a.m. and that the militants who stormed the living quarters almost immediately separated out the foreigners. (None of those interviewed would allow their last names to be used, fearing trouble for themselves or their families.)

Mohamed, a 37-year-old nurse, said at least five people were shot to death, their bodies still in front of the infirmary when he left Thursday night.

Chabane, who worked in the food service, said he bolted out the window and was hiding when heard the militants speaking among themselves with Libyan, Egyptian and Tunisian accents. At one point, he said, they caught a Briton.

"They threatened him until he called out in English to his friends, telling them, `Come out, come out. They're not going to kill you. They're looking for the Americans.' A few minutes later, they blew him away," Chabane said.

On Friday, it became clear the Algerian forces had retaken only the living quarters. 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.


Schemm reported from Rabat. Associated Press writers Aomar Ouali in Algiers, Oliver Teves in Manila, Philippines and Jan M. Olsen in Copenhagen contributed to this report.