ALGIERS, Algeria -- In a bloody, tragic finale, Algerian special forces stormed a natural gas complex in the Sahara desert Saturday to end a standoff with Islamist extremists that left at least 23 hostages dead and killed all 32 militants involved, the Algerian government said.
Algerian forces freed 107 foreigners and 685 Algerian workers, the country's Ministry of Interior said in a statement.
The dead may have included as many as six Britons and five Norwegians and at least one American.
Frederick Buttaccio from Katy, Texas is among the known dead.
Officials from those countries said they still lacked definitive information.
Citizens of Colombia, France and Malaysia were also either confirmed dead or missing.
Over four tense days, radical Islamists linked to al-Qaida held the Ain Amenas complex, which contained hundreds of plant workers from all over the world. The siege was punctuated by gun battles between the terrorists and the Algerian military and by dramatic escapes.
Late Saturday, President Barack Obama said in a statement that the blame lay with the terrorists.
"This attack is another reminder of the threat posed by al-Qaida and other violent extremist groups in North Africa," Obama said. "In the coming days, we will remain in close touch with the government of Algeria to gain a fuller understanding of what took place so that we can work together to prevent tragedies like this in the future."
The State Department Saturday night warned American citizens about the risks of travel to Algeria and is authorizing the families of State Department staff to leave the country if they choose.
The agency cited credible threats of the kidnapping of Western nationals and says there is a high threat of terrorism and kidnappings in Algeria.
French President Francois Hollande said the hostages were "shamefully murdered" by their captors, and said the episode lends further justification to France's military operation against al-Qaida-backed rebels in neighboring Mali.
In the final assault, the remaining band of militants killed the hostages before 11 of them were in turn cut down by the special forces, Algeria's state news agency said. The military launched its final assault to prevent a fire started by the extremists from engulfing the complex and blowing it up, the report added.
Ruben Andrada, 49, a Filipino civil engineer who works as one of the project management staff for the Japanese company JGC Corp., said he and his colleagues were used as human shields by the kidnappers, which did little to deter the Algerian military.
On Thursday, about 35 hostages were loaded into seven SUVs to move them from the housing complex to the refinery, Andrada said. The vehicle overturned, allowing him and a few others to escape.
An Algerian who asked not to be identified said he was hiding when he heard the militants speaking among themselves. 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,' " the Algerian said. "A few minutes later, they blew him away."
With Bloomberg News