An Algerian military raid to free hostages from at least 10 countries and wipe out their Islamist militant captors unleashed bloody chaos at a remote Sahara natural gas complex, and the British government said the operation was not yet over.
The fate of the fighters and many of the captives remained uncertain amid dueling claims from the Algerian military and the Islamists. Leaders around the world whose citizens were kidnapped by the militants expressed strong concerns about how Algeria was handing the situation.
Algeria's government said the raid was over late Thursday night. But both Britain's Foreign Office and US officials said Friday the desert conflict with the terrorists was ''ongoing."
Manuel Valls, France's interior minister, said the situation remained murky.
At least six people, and perhaps many more, were killed - among them Britons, Filipinos and Algerians. Terrorized hostages from Ireland and Norway trickled out of the Ain Amenas plant, 1,300 kilometers south of Algiers, the capital.
Dozens more energy workers remained unaccounted for - Americans, Britons, French, Norwegians, Romanians, Malaysians, Japanese, Algerians - as well as the fighters themselves.
"This remains a fluid and evolving situation and many details are still unclear, but the responsibility for the tragic events of the last two days squarely rests with terrorists who chose to attack innocent workers, murdering some and holding others hostage," British Foreign Secretary William Hague told Sky News.
Algeria's army-dominated government, hardened by decades of fighting Islamist militants, shrugged aside foreign offers of help and drove ahead alone, keeping a tight control of information even to Western leaders.
On Friday, Algeria's ambassador to Japan was summoned and told that Japan demanded that Algeria prioritize hostages' lives and cooperate more closely.
Prime Minister David Cameron spoke twice to his Algerian counterpart on Thursday and was "prepared for bad news," Britain's Foreign Office said.
A US official said while some Americans escaped, other Americans were either still held or unaccounted for. Defense Secretary Leon Panetta was briefed early Friday, according to a senior defense official, who offered no other details because "we view it as a sensitive, ongoing situation."
The officials spoke on condition of anonymity because they authorized to discuss the matter publicly.
The US government sent an unmanned surveillance drone to the BP-operated site, near the border with Libya, but it could do little more than watch Thursday's military intervention.
With the hostage drama entering its second day Thursday, Algerian security forces moved in, first with helicopter fire and then special forces, according to diplomats, a website close to the militants, and an Algerian security official.
The government said it was forced to intervene because the militants were being stubborn and wanted to flee with the hostages.
The militants said the helicopters opened fire when they were trying to move the hostages from the plant's housing complex to the main factory area, where other hostages were. The group - led by a Mali-based al-Qaida offshoot known as the Masked Brigade - suffered losses in Thursday's military assault - but garnered a global audience.
Even violence-scarred Algerians were stunned by the brazen hostage-taking Wednesday, the biggest in northern Africa in years and the first to include Americans as targets. Mass fighting in the 1990s had largely spared the lucrative oil and gas industry that gives Algeria its economic independence and regional weight.
Casualty figures in the Algerian standoff varied widely. The remote location is extremely hard to reach and was surrounded by Algerian security forces - who, like the militants, are inclined to advertise their successes and minimize their failures.
"An important number of hostages were freed and an important number of terrorists were eliminated, and we regret the few dead and wounded," Algeria's communications minister, Mohand Said Oubelaid, told national media, adding that the "terrorists are multinational," coming from several different countries with the goal of "destabilizing Algeria, embroiling it in the Mali conflict and damaging its natural gas infrastructure."
The official news agency said four hostages were killed in Thursday's operation, two Britons and two Filipinos. Two others, a Briton and an Algerian, died Wednesday in the initial militant ambush on a bus ferrying foreign workers to an airport. Citing hospital officials, the APS news agency said six Algerians and seven foreigners were injured.
APS said some 600 local workers were safely freed in the raid - but many of those were reportedly released the day before by the militants themselves.
The militants, via a Mauritanian news website, claimed that 35 hostages and 15 militants died in the helicopter strafing. A spokesman for the Masked Brigade told the Nouakchott Information Agency in Mauritania that only seven hostages survived.
President Barack Obama and Cameron spoke on the phone to share their confusion. White House Press Secretary Jay Carney said the Obama administration was "seeking clarity from the government of Algeria."
Militants earlier said they were holding seven Americans, but the administration confirmed only that Americans were among those taken.
BP, the Norwegian company Statoil and the Algerian state oil company Sonatrach, operate the gas field and a Japanese company, JGC Corp, provides services for the facility.
One Irish hostage managed to escape: electrician Stephen McFaul, who'd worked in North Africa's oil and natural gas fields off and on for 15 years. His family said the militants let hostages call their families to press the kidnappers' demands.
"He phoned me at 9 o'clock to say al-Qaida were holding him, kidnapped, and to contact the Irish government, for they wanted publicity. Nightmare, so it was. Never want to do it again. He'll not be back! He'll take a job here in Belfast like the rest of us," said his mother, Marie.
Dylan, McFaul's 13-year-old son, started crying as he talked to Ulster Television. "I feel over the moon, just really excited. I just can't wait for him to get home," he said.
At least one Filipino managed to escape and was slightly injured.
Algerian Interior Minister Daho Ould Kabila said the 20-odd militants entered the country from nearby Libya in three vehicles, in an operation commanded by extremist mastermind Moktar Belmoktar, who is normally based in Mali.
The militants made it clear that their attack was in revenge for the French intervention against Islamists who have taken over large parts of neighboring Mali.
France has encountered fierce resistance from the extremist groups in Mali and failed to persuade many Western allies to join in the actual combat.