PARIS -- Islamist militants seized a foreign-operated gas field in Algeria early Wednesday and took 20 or more foreign hostages, including Americans, according to an Algerian government official and the country's state-run news agency, in what appeared to be a retaliation for the French-led military intervention in neighboring Mali.
The Algerian agency said at least two people had been killed in the gas-field seizure, including one British national, and that the hostages included American, British, French, Norwegian and Japanese citizens.
Victoria Nuland, a State Department spokeswoman, told reporters in Washington that an unidentified number of American citizens were believed to be among the hostages, and Defense Secretary Leon E. Panetta, traveling in Italy, seemed to raise the possibility that the United States might take military action in response.
"By all indications this is a terrorist act," Mr. Panetta said. "It is a very serious matter when Americans are taken hostage along with others." He also said: "I want to assure the American people that the United States will take all necessary and proper steps that are required to deal with this situation."
The exact number of people being held was still far from certain. A top Algerian government official said 20 Islamist militants had attacked the gas field and that security services had now "encircled the base" so that "no one can leave." Concerning the number of hostages, he said that "the situation is confused for the moment," and that there might be as many as 30. "We don't have precise figures for now."
As for the 20 attackers, he said, they came heavily armed, in three unmarked vehicles. "That's how they slipped through," he said.
All told, up to 40 workers could be held hostage, according to oil company officials with interest in the field. A Japanese official confirmed that Japanese nationals were involved, and the Irish Foreign Ministry said one Irish citizen had been kidnapped. Some news agencies said as many as 41 hostages were seized.
The attack on the gas field appeared to be the first retribution by the Islamists for the French armed intervention in Mali last week, potentially broadening the conflict beyond Mali's borders and raising the possibility of drawing an increasing number of foreign countries directly into the conflict. Western officials had long warned that a Mali intervention, designed to halt an Islamist militant advance in that country, could incite a backlash far beyond Mali's borders.
Algeria, which has its own long history of fighting Islamic militancy, suggested it would show no tolerance for the gas-field attackers.
"The Algerian authorities will not respond to the demands of the terrorists and will not negotiate," Algeria's interior minister, Daho Ould Kablia, was quoted as saying by the official news agency.
The attack occurred at the fourth largest gas development in Algeria, In Amenas, and at its gas compression plant, which is operated by BP, the Norwegian company Statoil and the Algerian national oil company Sonatrach.
Bard Glad Pedersen, a Statoil spokesman, said that of 17 Statoil employees working in the field, only four were able to safely escape to a nearby Algerian military camp. "There is a hostage situation," he said. "We do not provide further information how we are dealing with the situation. Our main priority is the safety of our colleagues."
The Sahara Media Agency of Mauritania, quoting what it described as a spokesman for the militants, said they were holding five hostages in a production facility on the site and 36 others in a housing area, and that there were as many as 400 Algerian soldiers surrounding the operation. But that information could not be confirmed, and the agency's report on the specifics of where the hostages were held raised questions about its credibility.
Fighters with links to Al Qaeda's African affiliate, Al Qaeda in the Islamic Maghreb, claimed responsibility for the attack, according to both Mauritanian and Algerian news agencies. They quoted militants claiming that the kidnappings were a response to the Algerian government's decision to allow France to use its airspace to conduct strikes against Islamists in Mali.
Islamist groups and bandits have long operated in the deserts of western Africa, and a collection of Islamists have occupied the vast expanse of northern Mali since last year. In retaliation for the French-led effort to drive them out, those groups, including Al Qaeda in the Islamic Maghreb, have pledged to strike against France's interests on the continent and abroad, as well as those of nations backing the French operations. In France, security has been reinforced at airports, train stations and other public spaces.
The militant groups are financed in large part through ransoms paid for the freeing of Western hostages, and regular kidnappings have occurred in the West African desert in recent years. Seven French nationals are presently being held there.
The attack on Wednesday was carried out by a "heavily armed" group of "terrorists" traveling aboard three vehicles, the Algeria Interior Ministry statement said, and targeted a bus transporting foreign workers to a nearby airport at 5 a.m.
Algeria, which shares a desert border of several hundred miles with Mali, has resisted the possibility of organizing an armed intervention into the Malian north, fearing that fighting could spill into Algeria or drive militants into the country. Indeed, Al Qaeda in the Islamic Maghreb, one of the militant groups now holding northern Mali, began as an insurgent group fighting the Algerian government in the 1990s. But Algeria has authorized French jets flying missions in Mali to cross Algerian airspace.
Oil and gas are central to the Algerian economy, accounting for more than a third of the country's gross domestic product, over 95 percent of its export earnings and 60 percent of government financial receipts. Large pipelines connect the In Amenas fields with the Skikda liquefied natural gas export terminal, one of two export port facilities that supply gas to France, Spain, Turkey, Italy and Britain. Pipelines from the field also connect with Italy and Spain. In recent years, Algeria was the third largest natural gas supplier to Europe after Russia and Norway, according to the United States Energy Department.
Algeria is also a major oil exporter to Europe and Asia, where its high quality light sweet crude fits perfectly with local refineries. The United States is traditionally a major importer of Algerian crude, although over the last few years much of those imports have been replaced by new oil production in American shale oil fields in North Dakota and Texas.
Algeria has traditionally been known as a secure place for foreign companies to work and invest. Sonatrach and the security forces put tight security around oil and gas facilities during the struggle with Islamic militants in the 1990s, a period when energy infrastructure was never a major insurgent target.
Scott Sayare reported from Paris, and Adam Nossiter from Bamako, Mali. Reporting was contributed by Clifford Krauss from Houston, Elisabeth Bumiller from Rome and Rick Gladstone from New York.world
This article originally appeared in The New York Times.