ALGIERS, Algeria - Islamists angry over Algeria's support for the French offensive in Mali attacked a gas field in southern Algeria, killing two people and seizing a number of hostages, including Westerners, Algeria's interior minister said Wednesday.
The Westerners, accompanied by Algerian security forces, were en route to Ain Menas Airport when they were attacked by another group of no more than 20 people, Diho Weld Qabliyeh told Algerian state television. The security forces returned fire, and the attackers withdrew to the base of the petroleum operation, some 3 kilometers away, he said.
Upon arrival at the base, he continued, the attackers "took in a number of Westerners and Algerians -- some people told us they were nine, some people told us 12."
U.S. State Department spokeswoman Victoria Nuland said Americans were among the hostages.
Accounts over the number differed.
An Algerian and a Westerner were killed in the attack, and two Westerners, two of the security forces and two guards from the base were wounded, Qabliyeh said.
Algerian media reported that a British national was among the fatalities.
Algerian military forces were surrounding the building holding the hostage-takers and the hostages, Qabliyeh said.
Late Wednesday, the hostage-takers released the Algerians being held but continued holding the Westerners, Algerian state television reported.
The group has issued demands, Qabliyeh said. "The authorities do not negotiate, no negotiations; we have received their demands, but we didn't respond to them," he added.
A Mauritanian news agency, Al Akhbar, said the attackers demanded in a news release an end to "brutal aggression on our people in Mali."
It cited "blatant intervention of the French crusader forces in Mali" and accused the world of having left Syria's people "groaning under the pressure of the butcher" President Bashar al-Assad.
The news release said they chose Algeria because the country's president, Abdelaziz Bouteflika, allowed French military forces to use Algerian air space in attacking Mali.
It put the number of hostages at "more than 40," including seven Americans, two French, two British and a number of other Europeans.
An Islamist group claiming responsibility for 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."
But the Algerian Press Service, citing a source from the provincial administration of Illizi, reported that "a little more than 20 foreign nationals are held hostage."
Some nine or 10 Americans were working at the field, and U.S. officials were trying to determine who had been abducted, a State Department official told CNN.
The source said the abductors were demanding that members of their group who are being held prisoner be released and sent to northern Mali. The official was not clear about where the prisoners were being held.
"The first priority is to gain understanding of what is happening," a senior U.S. official with direct knowledge of the matter said. "We are working on ways to improve that now."
The official added that a Special Operations team -- the Commanders In-extremis Force -- "is on a very short string." In addition, he said, "other nations are similarly assessing their response posture."
He continued that "another important piece will be for Libya to really lock down the nearby border on their side," so personnel and weapons cannot get through.
Defense Secretary Leon Panetta, in Europe meeting with NATO allies, called the hostage-taking "a terrorist attack."
A spokesman for the group -- the name of which was translated as "those who sign with blood" -- said that the jihadists controlled the plant.
Saying that the operation was an act of revenge against Algeria, the spokesman said 400 Algerian soldiers were on the site "who have not been targeted by jihadists."
A spokesman for the Norwegian Prime Ministers' office told 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 were caught up in the incident.
Ireland's foreign minister said there were reports that an Irish citizen was involved; the office of the French president refused comment on reports that French citizens were 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 were occupying the site.
Statoil Executive Vice President Lars Christian Bacher said 17 of its employees -- 13 of them Norwegian -- were in or around the facility at the time of the attack. "We have received information that five of the 17 are brought to safety in a military camp in the area," he said in a statement.
Four are Norwegian and one is a Canadian resident; two people were injured and have received medical treatment, he said.
center for relatives has been set up in Bergen, Norway, he said.
The gas field lies about 60 kilometers west of the Libyan border and some 1,300 kilometers from the capital, Algiers, BP said.
The attack comes four days after Libyan, Algerian and Tunisian prime ministers reached security agreements Saturday in a summit in Libya, where they agreed to work together against terrorist threats.
In a statement, Rep. Ed Royce, R-California, called the attack "the latest demonstration of a large and growing radical movement across North Africa" and said the French "have acted appropriately" in intervening in Mali.
"Al-Qaeda in the Islamic Maghreb and its offshoots have been conducting regular kidnappings for years -- financing much of its operations through ransoms, earning millions," the chairman of the House Foreign Affairs Committee said.
"The network has planted deep roots in Europe. In recent years, cells have been broken up by authorities in France, Germany, Italy, Spain and Switzerland. In Mali, its brethren are imposing the strictest interpretation of Islamic law -- banning music and chopping off limbs. Large amounts of weapons are flowing into the region."