BAMAKO, Mali -- Dozens of foreign hostages may still be held by Islamist extremists who have defied demands to surrender in a besieged Algerian gas-field complex, Algeria's state-run news agency reported Friday, and the United States said for the first time that American citizens were among them.
Twelve Algerian and foreign workers have been killed since Algerian special forces began an assault against the kidnappers, the state news agency reported, citing an unnamed security official. It was the highest civilian death toll Algerian officials have provided in the aftermath of the assault, which freed captives and killed kidnappers but also left some hostages dead.
Previous unofficial estimates of the foreign casualties have ranged from 4 to 35.
The Algerian news agency said that the country's special forces were seeking to reach a "peaceful solution" with the remnants of a "terrorist group" that was still holding hostages in the refinery area of the gas field in remote eastern Algeria. It also gave a new sense of how many people may have been at the facility when the militants seized it on Wednesday, asserting that nearly 650 had managed to leave the site since then, including 573 Algerians and nearly half of the 132 foreigners it said had been abducted.
But that still left many people unaccounted for, adding to the global concern about the fate of the hostages, who come from as many as 10 different nations, in one of the biggest mass-abductions of foreign workers in years.
Secretary of State Hillary Rodham Clinton, addressing the crisis in Washington following a meeting with Foreign Minister Fumio Kishida of Japan, suggested Algeria's operation to end it was far from over.
"This is an extremely difficult and dangerous situation," she told reporters. Describing a telephone conversation she had earlier Friday with Algeria's prime minister, Abdelmalek Sellal, Mrs. Clinton said she had emphasized to him that "the utmost care must be taken to preserve innocent life."
Earlier Friday the State Department spokeswoman, Victoria Nuland, said that not all Americans had been freed. "We have American hostages," Ms. Nuland told reporters, offering the government's first update on what is known about the Americans since officials confirmed on Thursday that seven or eight Americans had been inside the gas-field complex.
Ms. Nuland also said the United States would not consider a reported offer made by the kidnappers to exchange two Americans for two prominent figures imprisoned in the United States -- Omar Abdel Rahman, a sheik convicted of plotting to bomb New York landmarks, and Aafia Siddiqui, a Pakistani woman convicted of shooting two American soldiers in Afghanistan. It was impossible to confirm that offer, which was reported by the Washington-based SITE Intelligence Group, a service that tracks jihadist activity on the Internet.
Intensifying the uncertainties, a spokesman for the militants, who belong to a group called Al Mulathameen, said Friday that they planned further attacks in Algeria, according to a report by the Mauritanian news agency ANI, which maintains frequent contact with militant groups in the region. The spokesman called upon Algerians to "keep away from the installations of foreign companies, because we will suddenly attack where no one would expect it," ANI reported.
A Pentagon official said an Air Force C-130 had left Algeria for an unidentified base in Europe, carrying a number of the rescued hostages but no Americans. The official said a second, larger evacuation plane, a C-17, was still on the ground in Algeria, and it was unclear how many rescued hostages would be boarded or when it would depart.
A separate hostage situation of sorts appeared to have been averted at a village in Mali, the neighboring country where a French military intervention to stop radical Islamists may have been the catalyst for the Algerian gas-field seizure by the Al Mulathameen group. But details were sketchy.
A senior French official in Paris said Malian Islamist fighters, threatened by French and Malian soldiers, had occupied the village, Diabaly, and were threatening to use residents as human shields if attacked. But by Friday evening, a local official in Diabaly said the Islamists and most of the villagers had fled. "There's practically nothing left in Diabaly except burned-out vehicles and boxes of ammunition," said the official, Benco Ba, a local parliamentary deputy.
The Algerian military operation at the gas field began on Thursday without consultation with the foreign governments whose citizens worked at the facility. It has been marked by a fog of conflicting reports, compounded by the remoteness of the facility, near a town called In Amenas hundreds of miles across the desert from the Algerian capital, Algiers, and close to the Libyan border.
Algeria's state radio, citing an official source, reported on Friday that 18 militants had been killed, the first precise death count offered by state media. The state news agency also suggested that hundreds of civilians "had been freed," though many of the employees inside the sprawling facility may have simply been on site at the time of the militant assault and were not necessarily being held by the kidnappers.
In London, Prime Minister David Cameron of Britain told Parliament the number of Britons at risk was estimated late Thursday at "less than 30." That number has now been "quite significantly reduced," he said, adding that he could not give details because the crisis is continuing. British officials have said they know at least one Briton was killed when the militants seized the facility.
Offering a broad account of Algeria's handling of the operation, he told lawmakers: "We were not informed of this in advance. I was told by the Algerian prime minister while it was taking place. He said that the terrorists had tried to flee, that they judged there to be an immediate threat to the lives of the hostages and had felt obliged to respond."
He added: "This is a large and complex site and they are still pursuing terrorists and possibly some of the hostages in other areas of the site. The Algerian prime minister has just told me this morning that they are now looking at all possible routes to resolving this crisis."
In Paris, Foreign Minister Laurent Fabius of France confirmed for the first time that a French citizen had been killed, although it was not clear exactly when. The victim, whom Mr. Fabius identified as Yann Desjeux, had contacted family as recently as noon Thursday, according to the French newspaper Sud Ouest, which also said it had spoken with Mr. Desjeux. Three other French citizens were involved in the hostage situation but are now in safety, Mr. Fabius said.
Frustration with Algeria's information vacuum seemed particularly vexing to Japan, where an energy company that had assigned 17 employees to the gas-field facility said Friday that seven were confirmed safe but 10 unaccounted for. Prime Minister Shinzo Abe personally had appealed to his Algerian counterpart on the phone early Friday to stop the military action, the Asahi Shimbun newspaper reported, but was told that military action was "the best response and we are continuing our operation."
Defense Secretary Leon E. Panetta met with Mr. Cameron in London as Pentagon officials were continuing to try to learn details about the raid.
"We are working around the clock to ensure the safe return of our citizens and we will continue to be in close consultation with the Algerian government," Mr. Panetta said in a speech in London before meeting with Mr. Cameron.
On Thursday, despite requests for communication and pleas to consider the safety of their abducted citizens, the United States, Britain and Japan said they had not been told in advance about the military assault, stirring frustration that the Algerians might have been overly aggressive and caused needless casualties. But the Algerian government, which has a history of violent suppression of Islamist militancy, stood by its decision to deal forcefully with the kidnappers.
"Those who think we will negotiate with terrorists are delusional," said the communications minister, Mohand Saïd Oublaïd. "Those who think we will surrender to their blackmail are delusional."
Citing information from Algerian officials, Mr. Cameron told Parliament that the kidnappers' attack began on Wednesday when "the terrorists first attacked two buses en route to the Amenas airfield before attacking the residential compound and the gas facility at the installation. It appears to have been a large, well-coordinated and heavily armed assault and it is probable that it had been preplanned."
The attackers took hostages at both the residential compound and at the gas plant itself, he said.
Earlier reports had suggested that the Algerian military struck when the assailants sought to move with their captives.
Stephen McFaul, 36, a hostage from Northern Ireland, told relatives that the kidnappers put explosives around his neck but that he was able to escape after Algerian forces attacked a convoy of five vehicles in which the abductors were seeking to transport their captives, according to his brother, Brian. Four of the vehicles were hit, but the one in which he Stephen McFaul was traveling crashed and he fled, the brother said.
The abductions were meant to avenge France's armed intervention in Mali, said Mr. Oublaïd, the Algerian communications minister. That conflict has escalated since French warplanes began striking Islamist fighters who have carved out a vast haven there.
The fighters had been prepared to attack the site for nearly two months, the militants' spokesman said, according to the ANI report, because they believed that the Algerian government, which has emerged in news reports as the focus of the group's anger, "was surely going to be the ally of France" in the Malian conflict.
As France was amassing reinforcements in Mali, aiming to reach 2,500 soldiers on the ground, the Malian Army said on Friday that its troops had retaken the central town of Konna, which Islamists seized at the beginning of the conflict.
BP, the Britain-based energy giant that jointly controls the gas installation in Algeria, said in a statement on Friday that there was a "small number of BP employees" at the facility "whose current location and situation remain uncertain." The company said it had flown out 11 of its staff members along with hundreds of employees of other oil companies on Thursday, and a fourth flight was scheduled to depart on Friday.
Statoil, the Norwegian company that helps manage the installation, reported that eight of its workers remained unaccounted for, while nine had escaped to safety over the last few days. "There is a still a hostage situation," said company executive vice president Lars Christian Bacher. Of the nine who had escaped, he added, "All of them have experienced extreme stress."
Adam Nossiter reported from Bamako and Alan Cowell and Scott Sayare from Paris. Reporting was contributed by Rick Gladstone from New York; Elisabeth Bumiller, Julia Werdigier and John F. Burns from London; Steven Erlanger from Paris, Eric Schmitt, Thom Shanker, David E. Sanger and Michael R. Gordon from Washington; Martin Fackler and Hiroko Tabuchi from Tokyo; Mayy El Sheikh from Cairo and Clifford Krauss from Houston.
This article originally appeared in The New York Times.