BAMAKO, Mali — The hostage crisis in the Algerian desert reached a bloody conclusion Saturday as the army carried out a final assault on the gas field taken over by Islamist militants, killing 11 of them, but only after they had executed seven hostages, the official Algerian news agency reported.
French, British, and US officials said the Algerian government had told them the military operation was over, but a senior Algerian government official said security forces were ‘‘doing cleanup’’ to make sure no kidnappers were hiding in the sprawling industrial complex.
Western officials deplored the loss of life during the four-day siege, which Philip Hammond, the British defense secretary, called ‘‘appalling and unacceptable.’’
Defense Secretary Leon Panetta, who appeared with Hammond at a news conference in London, said he did not yet have reliable information about the fate of Americans at the facility, although the Algerian official said two had been found ‘‘safe and sound.’’
In keeping with the Algerian government’s relative silence throughout the crisis — in which some Western hostages were reported summarily shot by kidnappers and others apparently killed in government assaults — there were few details Saturday about how the final act unfolded.
But the provisional death toll, even by the government’s reckoning, was heavy. Out of dozens taken hostage, 23 were dead while 32 kidnappers were killed, according to the government news service.
The government said it had recovered machine guns, rocket launchers, suicide belts, and small arms.
The Algerian news agency report did not give the nationalities of the hostages it said were executed Saturday, and it remained unclear if there were other hostages at the remote plant and whether they were alive. Earlier news reports said at least 10 and as many as dozens of hostages from several nations were in the hands of the kidnappers as of Friday.
US officials had said that ‘‘seven or eight’’ Americans had been at the In Amenas field when it was seized by the militants on Wednesday.
One American, Frederick Buttaccio, 58, of Katy, Texas, was confirmed dead on Friday, and the French government said one of its citizens, identified as Yann Desjeux, had also died before Saturday’s raid. Britain earlier said at least one of its citizens was killed, and an Algerian state news agency said Algerians had also been killed as of Friday.
The Algerian official, who would speak only on the condition of anonymity, said a precise tally of the dead would take time. ‘‘There are corpses that are totally charred,’’ he said. ‘‘We’ve got to do identification work. It’s very difficult.’’ Algerian officials have said some of the kidnappers blew themselves up.
The Algerian news agency said the militants had set fire to part of the complex Friday night, which prompted the military assault Saturday. The raid, if it swept up all the attackers, would bring to an end a siege involving dozens of hostages and kidnappers that drew criticism from Western governments for the tough manner in which it was handled by the Algerian security services.
A militant who claimed responsibility for the attack, and who was blamed by the Algerians for leading it, Mokhtar Belmokhtar, was until recently a leading commander of Al Qaeda’s North and West African branch, Al Qaeda in the Islamic Maghreb.
One Algerian who managed to escape told France 24 television late Friday night that the kidnappers said, ‘‘We’ve come in the name of Islam, to teach the Americans what Islam is.’’
The haggard-looking man, interviewed at the airport in Algiers, said the kidnappers then immediately executed five hostages.
The militants who attacked the plant said it was in retaliation for French troops sweeping into Mali this month to stop an advance of Islamist rebels south toward the capital. However, the militants later said they had been planning an attack in Algeria for two months on the assumption that the West would intervene in Mali.
The Algerian state oil company, Sonatrach, said Saturday that the attackers had evidently mined the facility with the intention of blowing it up and that the company was working to disable the mines.
The Algerian government has rejected the criticism of its go-it-alone approach, toughest from the British and Japanese governments whose nationals were among those kidnapped, saying they have had years of experience dealing with terrorist attacks.
The Algerian government has also denied that it started the confrontation, saying troops, who began their assault by firing on a convoy, were merely responding to the militants’ attempts to leave the field with hostages.
The government official, however, acknowledged Saturday that the militant attack was of a scale and complexity the country had not experienced
“This was a multinational operation,’’ he said of the kidnappers. ‘‘They’ve come from all over, Tunisia, Egypt, Mauritania. It’s the first time we’ve handled something on this scale.’’