Several Western hostages reported killed in Algeria siege operation Western hostages being held by Islamist militants at a gas plant in Algeria were feared to have been killed with reports of several casualties from a raid by Algerian forces Thursday. The gas plant near In Amenas, Algeria. An "ongoing operation" was under way at the remote desert facility where dozens of workers - including three Americans - were being held, Britain's Foreign Office said. It gave no further details. Unconfirmed reports from local sources cited by Reuters and The Associated Press said hostages and militants had been killed in the operation. Earlier, some of those being held reportedly escaped from the plant, near In Amenas, close to the Libya border. U.S. officials could not confirm nor deny any of the reports, saying information on the situation was "murky." An Ireland government spokesman said Thursday that an Irish national held at the In Amenas gas plant had "made contact with his family and is understood to be safe and well, and no longer a hostage." Islamists stormed the natural gas pumping site and workers' housing before dawn on Wednesday and claimed to have seized 41 foreign workers - from countries including the United States, France, Ireland, Britain, Japan and Norway - and local employees. The Associated Press, citing claims from militants, said the site was attacked on Thursday morning by Algerian military helicopters. It reported: Islamist militants have told a Mauritanian news outlet that Algerian military helicopters strafed the gas complex where they are holding hostages, killing 35 of the foreigners and 15 of the kidnappers. The spokesman for the Masked Brigade, which had earlier claimed responsibility for the assault Wednesday on the gas complex deep in the Sahara desert, said Thursday that Abou El Baraa, the leader of the kidnappers, was also killed in the helicopter attack. The information came from the Nouakchott Information Agency, which has often carried reports from al-Qaida-linked extremist groups. A local resident near the plant told Reuters the Algerian military had opened fire, and that "many people" were killed: The resident, who asked not to be identified, said there were many bodies at the scene. He did not give firm numbers of the dead or say whether they were kidnappers, hostages or both. French wire service Agence France Press also said an Algerian helicopter was attacking the facility. Twenty hostages of an Algerian militant group with ties to al Qaeda in a standoff with the Algerian Army are reported to have escaped Thursday. Over 41 hostages of several nationalities, including Americans, were being held in a BP gas facility. Faycal Metaqui, a journalist at Algerian newspaper El Watan, told French news channel BFM there was "much confusion" over information from the hostage site. He said he was unable to confirm with authorities the earlier reports that some hostages had escaped. "Sadly, there have been some reports of casualties but we are still lacking any confirmed or reliable information," said a statement from oil giant BP, which is a joint owner of the plant. "This is a dangerous and rapidly developing situation," U.K. Foreign Secretary William Hague told reporters in Sydney Thursday. The crisis - one of the biggest international hostage incidents in decades - opened an international front in the civil war in neighboring Mali after French troops launched an offensive against Islamist rebels linked to al-Qaida in that country. The group that has claimed responsibility for the Islamists' raid is said to be led by a jihadist called Mokhtar Belmokhtar, a cigarette smuggler whose nicknames range from "The Uncatchable" and "Mister Marlboro." The militants have demanded an end to the French military campaign in Mali, where hundreds of French paratroopers and marines are launching a ground offensive against rebels a week after Paris began firing on militants from the air. In France, President Francois Hollande declined to give any further information about the Algerian operations. "The best is to say the least," he said. What counts is to allow the Algerians to be able to liberate [the hostages]. In Mali, land of 'gangster-jihadists,' ransoms help fuel the movement Nancy Ing, Jim Miklaszewski and Courtney Kube, NBC News, contributed to this report.