ISLAMIST extremists "executed" seven hostages yesterday before a final, bloody assault by the Algerian army ended a four-day siege in the desert.
In all, 23 hostages and all 32 terrorists had died, while 107 foreign workers and 685 local employees were released.
BP said last night that four of its employees were still missing several hours after a dramatic firefight inside the gas plant that left 11 terrorists dead.
America prepared to unleash its drones as a manhunt was stepped up for the fanatic behind the siege.
The final assault on the gas processing complex began in the middle of the morning, ending a hiatus of almost 48 hours after the first attempt by Algerian forces to overpower the terrorists.
Security sources said the al-Qaeda militants' last stand was in a factory or workshop area of the Tigantourine gas plant, which they had held since Wednesday.
The group of about 40 men from the Masked Brigade, also known as Witnesses in Blood, had captured foreign workers in a residential area of the sprawling complex before being cornered in the main plant, about two miles away.
After a two-day standoff, Algeria's special forces – known as the Ninjas – made a final assault. Reports suggested they reacted to gunfire and the execution of prisoners, although it may also be that they lost patience.
A security source said: "Eleven terrorists lost their lives along with the foreign hostages. We think they [the hostages] were killed in retaliation."
Official sources told Algeria's El Watan newspaper, a journal known for its close contact with the country's secret services, that the terrorists had tried to set fire to the gas facility's installations on Friday night after their demands – including safe passage and the release of al-Qaeda terrorists in the US – remained unmet.
El Watan claimed: "On Saturday morning, the terrorists had lost all hope of leaving the facility with the last seven hostages and had begun to execute some of the hostages, forcing the Algerian special forces to intervene. In fact the terrorists were preparing for an act of collective suicide."
Those who perished include Abdul Rahman al Nigeri, who led the ground attack. In what appeared to be his final words he was heard narrating the advance of the Algerian forces to the sound of ever-closer gunfire in a video posted briefly online.
"Half of the brothers have been killed along with 35 hostages," he said. "There are some hostages who are still alive and they are with some of our brethren in the gas factory. I swear we will blow them up. Now they [Algerian forces] are coming towards us. God is the greatest!"
As gunfire rings out, seemingly killing his colleagues, his last words are: "They are dead, may God have mercy on their souls. We are drawing together all those armed [fighters] who have hostages."
But the operation's mastermind, Mokhtar Belmokhtar, remains at large and is now the centre of an international manhunt.
The Pentagon is understood to have authorised the use of drones to track and kill Belmokhtar, who is believed to be in northern Mali.
US Defence Secretary Leon Panetta, speaking in London, said that nobody was going to attack the US and get away with it. "We have made a commitment that we're going to go after al-Qaeda wherever they are and wherever they try to hide," he said. "We have done that obviously in Afghanistan, Pakistan, we've done it in Somalia, in Yemen and we will do it in North Africa as well."
The full extent of the militants' chilling intent and the horrors inside the facility began to emerge yesterday.
One source said 15 burned bodies were discovered by Algerian troops as they secured the area. Another said 16 hostages had been freed, including two Americans, two Germans and a Portuguese. French authorities said all their nationals were accounted for, while Norway said six of its citizens were missing and the Romanian government said one of its citizens was dead. William Hague, the British foreign secretary, said five Britons were either dead or unaccounted for last night.
Algeria's interior minister said the attackers – as many as 40 men armed with rocket launchers and machine guns – were under the direct supervision of Belmokhtar, a one-eyed Algerian militant linked to al-Qaeda.
He has combined his long-running campaign against the Algerian government with a lucrative smuggling and kidnapping operation across the Sahara.
Photographs of workers kneeling in the desert, their hands above their heads and surrendering to gunmen on Wednesday, emerged last night. The images shown by Algeria's Ennahar Television displayed hostages at the mercy of the Islamist gunmen.
The number of men in the pictures underlined the scale of the hostage-taking by the militants. At one point they were holding more than 600, Algerian officials said.
They allowed locals to go free, saying they did not want to hurt Muslims. Some had to recite parts of the Koran to prove they followed Islam.
BP said that four employees remained unaccounted for, with 14 confirmed safe, two of whom had sustained non-life-threatening injuries.
Bob Dudley, BP's chief executive, said: "Our focus remains on our colleagues who we have not yet been able to locate and on supporting their families through a time of agonising uncertainty . . . This is a difficult and sad time for us all."
Those hostages who had been rescued or escaped began to tell dramatic accounts of the siege.
Ruben Andrada, 49, a Filipino civil engineer, was forced to wear a "bomb necklace" before making a break for freedom. "There was shooting all around," he said.
He suffered cuts and bruises and was grazed by a bullet on his right elbow.