Story highlights Two Americans unaccounted for, senior U.S. official says 
 
 Obama says "scourge of terrorism" must be fought 
 
 Algerian state news: At least 55 people, including hostages and militants, have died 
 
 The militants targeted an eastern Algerian gas facility where many foreigners workers 
 
 Algerian troops ended a hostage crisis at a remote gas facility Saturday with one last, bloody assault, Algerian and Western officials said, after three days of chaos and confusion left dozens dead and fanned fears of a new terror front in Africa. At least 23 hostages and 32 "terrorists" were killed around the sprawling facility in eastern Algeria's desert, the Algerian interior ministry said Saturday. Initial reports from Algerian state news media said that seven workers had been executed during the army’s raid, but the senior government official and another high-level official, both of whom spoke on the condition of anonymity, later said the number killed and the cause were unknown. The saga closed after a "final" assault, which itself contributed to the deaths of seven hostages and 11 militants, according to Algerian state media reports. Britain’s foreign secretary, William Hague, said that five Britons and one British resident had died in the final rescue attempt or were unaccounted for. In a brief statement released early Saturday night the president said his administration would “remain in close touch with the government of Algeria to gain a fuller understanding of what took place.” 
 
 The British defense minister, Philip Hammond, called the loss of life “appalling and unacceptable” after reports that up to seven hostages were killed in the final hours of the hostage crisis, and he said that the leaders of the attack would be tracked down.
– The Algerian hostage standoff appears to be over after four days, but the end came with more bloodshed: The government says kidnappers executed seven hostages during this morning's "final assault." That brings the death toll to at least 32 "terrorists" and 23 hostages, including one American, report AP and CNN. No details are out yet on nationalities of the latest victims. "In principle, it's over," a government official tells the New York Times. Only a "clean-up process" remains. A Turkish official says two remaining American hostages were found "safe and sound." Algeria's state news agency reports that another 11 of the al-Qaeda-linked militants were killed in the raid, but it did not say whether any remained alive. As for that "clean-up process": The militants reportedly booby-trapped the entire gas refinery with explosives, and Algerian troops had begun the painstaking task of clearing them.