U.S. Defense Secretary Leon Panetta, speaking in London, said the United States was working round the clock to ensure the safe return of its citizens.

Those freed include some Americans, while other U.S. nationals are still unaccounted for, U.S. officials said.

Meanwhile, the United States is evacuating 10 to 20 people caught up in the crisis, a U.S. defense official told CNN on Friday. They will be taken to U.S. facilities in Europe, the official said, where the condition of those injured can be assessed.

Britain has sent trauma experts and consular affairs officers who can issue emergency passports to a location about 450 kilometers (280 miles) away from the besieged plant, a Foreign Office official said, so they'll be "as close" as possible to the scene.

BP said Friday that a "small number of BP employees" were unaccounted for. The same held for some workers with Statoil, though nine others with the company -- including five who escaped -- are safe. Four Norwegians and a Canadian with that oil firm are in an airport hotel in Bergen, Norway, after being transported from Algeria, Statoil spokeswoman Sissel Rinde said.

Both BP and Statoil -- two of the foreign companies with In Amenas operations -- are pulling personnel from Algeria, which is Africa's largest natural gas producer and a major supplier of natural gas to Europe.

BP said it had flown 11 of its employees and several hundred staff from other companies out of the North African country Thursday and expected another flight Friday.

Mark Cobb, a Texan who has a LinkedIn profile identifying him as general manager for a BP joint venture out of In Amenas, told CNN he was "safe," having escaped on "the first day," though he didn't elaborate.

A U.S. military C-130 plane flew 12 wounded in the ordeal out of Algeria earlier Friday, a U.S. defense official said. None of them were Americans, though efforts continue to evacuate freed Americans.

Three workers for a Japanese engineering company that was working on the site have been contacted and are safe, said Takeshi Endo, a senior manager for JGC Corp. But the company had not been able to contact 14 others, he said.

France's foreign ministry said that, in addition to one death, three of its citizens were rescued.

Japan 'terribly disappointed' in Algerian military operation

Algeria faces tough questions from governments of kidnapped nationals over its handling of the crisis. Neither the United States nor Britain, for instance, were told in advance about Algeria's military operation Thursday.

Japanese Chief Cabinet Secretary Yoshihide Suga said his nation's officials urged Algeria's government to avoid exposing hostages to danger. Japanese Vice Minister Shunichi Suzuki summoned Algeria's ambassador Friday to express Tokyo's concern

"We are terribly disappointed about the Algerians' military operation," Suga said.

U.S. officials offered a similar plea to the Algerians, urging them to be cautious and make the hostages' safety their first priority, an official in President Barack Obama's administration said.

A senior U.S. official said U.S. officials did not trust information they got from the Algerians, "because we hear one thing and then we hear something else."

But Algeria acted out of a sense of urgency, Communications Minister Mohamed Said told state television, after noticing hostages being moved toward "a neighboring country," where kidnappers could use them "as a means of blackmail with criminal intent."

Algerian troops fired on at least two SUVs trying to leave the facility, Algerian radio said. And a reporter saw clashes near the site, according to the Algerian Press Service and radio reports.

"There were a number of dead and injured, we don't have a final figure," the communications minister said of casualties following the operation.

Belmoktar, the man behind the group claiming responsibility for the attack and kidnappings, is known for seizing hostages.

French counterterrorism forces have long targeted Belmoktar, an Algerian who lost an eye fighting in Afghanistan in his teens. Libyan sources said he spent several months in Libya in 2011, exploring cooperation with local jihadist groups and securing weapons.

The militants said they carried out the operation because Algeria allowed French forces to use its airspace in attacking Islamist militants in Mali. Media in the region reported the attackers issued a statement demanding an end to "brutal aggression on our people in Mali" and cited "blatant intervention of the French crusader forces in Mali."

French Prime Minister Jean-Marc Ayrault said the Algerian hostage situation "confirms the gravity of the terrorist threat and the necessity to fight it with a determined and united front."

That sentiment was echoed by Clinton, the top U.S. diplomat. She stressed the need for a concerted, international effort to address terrorist and other threats around Africa.

"It is absolutely essential that, while we work to resolve this particular terrible situation, we continue to broaden and deepen our counterterrorism cooperation," she said Friday. "It is not only cooperation with Algeria, it is international cooperation against a common threat."