Updated 6:52 p.m. ET
ALGIERS, Algeria Algerian helicopters and special forces stormed a gas plant in the stony plains of the Sahara on Thursday to wipe out Islamist militants and free hostages from at least 10 countries being held inside. Bloody chaos ensued, leaving the fate of the fighters and many of the captives uncertain.
Dueling claims from the military and the militants muddied the world's understanding of an event that angered Western leaders, raised world oil prices and complicated the international military operation in neighboring Mali.
At least six people, and perhaps many more, were killed - Britons, Filipinos and Algerians. Terrorized hostages from Ireland and Norway trickled out of the Ain Amenas plant, families urging them never to return.
Dozens more remained unaccounted for: Americans, Britons, French, Norwegians, Romanians, Malaysians, Japanese, Algerians and the fighters themselves.
One high-ranking source in the U.S. government told CBS News four Americans have been freed tonight, one of them injured, after the assault, although that number hasn't been confirmed.
The U.S. government sent an unmanned surveillance drone to the BP-operated site, near the border with Libya and 800 miles from the Algerian capital, but it could do little more than watch Thursday's intervention. Algeria's army-dominated government, hardened by decades of fighting Islamist militants, shrugged aside foreign offers of help and drove ahead alone.
A senior administration official told CBS News correspondent Major Garrett the U.S. government was not made aware of the Algerian rescue raid in advance. Before the raid, top U.S. officials "urged" Algeria to be "cautious" and "strongly encouraged" Algeria to establish safety of the hostages as their "top priority."
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 - led by a Mali-based al-Qaeda offshoot known as the Masked Brigade - suffered losses in Thursday's military assault, but succeeded in garnering 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.
The hostage-taking raised questions about security for sites run by multinationals that are dotted across Africa's largest country. It also raised the prospect of similar attacks on other countries allied against the extremist warlords and drug traffickers who rule a vast patch of desert across several countries in northwest Africa. Even the heavy-handed Algerian response may not deter groups looking for martyrdom and attention.
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 an 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.
By nightfall, Algeria's government said the raid was over. But the whereabouts of the rest of the plant workers was unclear.
President Barack Obama and British Prime Minister David 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."
An unarmed American surveillance drone soared overhead as the Algerian forces closed in, U.S. officials said. The U.S. offered military assistance Wednesday to help rescue the hostages but the Algerian government refused, a U.S. official said in Washington. He spoke on condition of anonymity because he was not authorized to speak publicly about the offer.