The reports of high casualties have disturbed foreign governments, prompting a number to criticize Algeria's operation. Britain's Foreign Office attempted to prepare the British public by saying, "We should be under no illusion that there will be some bad and distressing news to follow from this terrorist attack."
Oil prices rose $1.08 on the news to $95.32 on the New York Mercantile Exchange and prompted energy companies like BP P.L.C. and Spain's Compania Espanola de Petroleos SA to try to relocate energy workers at other Algerian plants.
The Algerian government said it was forced to intervene due to the militants' stubbornness and their desire to flee with the hostages.
"An important number of hostages were freed and an important number of terrorists were eliminated, and we regret the few dead and wounded," Algerian 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."
Islamists from the Masked Brigade, a Mali-based al-Qaeda offshoot, who have been speaking through a Mauritanian news outlet, said Algerian helicopters opened fire as the militants tried to leave the vast energy complex with their hostages. They claimed that 35 hostages and 15 militants died in the attack and only seven hostages survived.
Algeria's official news service, meanwhile, earlier claimed that 600 local workers were freed in the raid and half of the foreigners being held were rescued. Many of those locals were reportedly released on Wednesday, however, by the militants themselves.
One Irish hostage was confirmed safe: supervising electrician Stephen McFaul, whose mother said he would not be returning to Algeria.
"He phoned me at 9 o'clock to say al-Qaeda 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.
In Washington, White House press secretary Jay Carney said the Obama administration was "concerned about reports of loss of life and are seeking clarity from the government of Algeria."
Japan's Prime Minister Shinzo Abe protested the military raid as an act that "threatened the lives of the hostages," according to a spokesman.
Jean-Christophe Gray, a spokesman for British Prime Minister David Cameron, said Britain was not informed in advance of the raid but described the situation as "very grave and serious." French President Francois Hollande called it a "dramatic" situation involving dozens of hostages.
Norwegian Prime Minister Jens Stoltenberg would not criticize the Algerian operation but said he wished the Norwegian government would have been notified before it started. He added that while Algeria has declined medical help, Norway will send a plane with medical equipment and personnel.
An unarmed American surveillance drone soared overhead as the Algerian forces closed in, U.S. officials said. The United States offered military assistance Wednesday to help rescue the hostages - whose numbers varied wildly from dozens to hundreds - but the Algerian government refused, a U.S. official said in Washington. He spoke on condition of anonymity.
Algerian forces who had ringed the Ain Amenas complex in a tense standoff had vowed not to negotiate with the kidnappers, who reportedly were seeking safe passage. Security experts said the end of the two-day standoff was in keeping with the North African country's tough approach to terrorism.
"I would not be surprised if the death toll was as high as the militants put it, it's a well-known fact that the Algerians never had problems causing a bloodbath to respond to terrorist attacks," said Riccardo Fabiani, North Africa analyst for the Eurasia group, who expressed doubt over Algeria's claims that mediation was abandoned in the face of the kidnappers' intransigence. "I wonder whether really in 24 hours you can establish some kind of negotiations with terrorists, I don't think they really tried."