Islamists take foreign hostages in attack on Algerian oil field Map: In Amenas, Algeria NEW: Panetta calls hostage-taking a "terrorist attack" Some Americans are among the hostages, the U.S. State Department says The In Amenas gas field is run jointly by BP, Statoil and Algeria's Sonatrac Algerian media report 2 dead (CNN) -- Islamists angry over Algiers' support for the French offensive in Mali attacked an Algerian gas field, caused casualties and seized more than 40 foreign hostages, North African media outlets reported Wednesday. At least one foreigner died in the terrorist attack on the In Amenas field near the Libyan border in the east, Algeria's Interior Ministry said Wednesday. Algerian media later reported a second person, a British national, was killed as well. U.S. State Department spokeswoman Victoria Nuland confirmed the incident and said some Americans were among the hostages, but gave no further details. She said the United States is in touch with Algerian authorities and closely monitoring the situation. The U.S. Embassy has issued an emergency message to U.S. citizens in that country to be careful, she said. Defense Secretary Leon Panetta, in Europe meeting with NATO allies, called the hostage-taking "a terrorist attack." An Islamist group claiming the attack told the Mauritanian News Agency and Sahara Media that 41 "Westerners including seven Americans, (as well as) French, British and Japanese citizens have been taken hostage." A spokesman for the group -- the name of which was translated as "those who sign with blood" -- said that the jihadists have been able to gain control of the plant. Stressing that the operation is an act of revenge against Algeria, the spokesman said that there are 400 Algerian soldiers on the site "who have not been targeted by jihadists." The terrorist group targeted a bus carrying passengers from a workers' base at the gas field to an airport, Algeria's Interior Ministry said. At least six people were injured, it said. When the early morning attack was repelled by guards, the group besieged part of the site and "captured an undetermined number of workers, including foreigners," it said. The nationality of the casualties is not yet clear. A spokesman for the Norwegian Prime Ministers' office confirmed to CNN that "13 Norwegians, all employees of Statoil, are involved in the incident at Amenas gas field in Algeria." The UK Foreign Office said British nationals are also caught up in the incident. Ireland's foreign minister said there are reports that an Irish citizen is involved, but the office of the French president has refused to comment on reports that French citizens are among the hostages. Oil giant BP, which operates the In Amenas field in a joint venture with Sonatrac, the Algerian national oil company, and Norway's Statoil, said it was attacked by "unidentified armed people" who are now occupying the site. The gas field lies about 60 kilometers (37 miles) west of the Libyan border and some 1,300 kilometers from the capital, Algiers, BP said. The Libyan, Algerian and Tunisian prime ministers reached security agreements on Saturday in a summit in Libya. They agreed to work together against terrorist threats. Criticism emerged on a Facebook page from jihadists in eastern Libya. They praised al-Shabaab in Somalia after the French failed hostage rescue, expressed support for the fighters in northern Mali and condemned the summit. Read related: U.S. supported France's failed hostage rescue in Somalia CNN's Carol Jordan, Laura Smith-Spark and Antonia Mortensen reported from London, Elise Labott from Washington, Joe Sterling and Yousuf Basil from Atlanta, Jomana Karadsheh from Tripoli, Libya; and Dheepthi Namasivayam from Paris.