An Algerian army operation to free hostages at a gas facility in the desert has left a number of Islamist militants and their captives missing.
State television is reporting that four foreign hostages had been killed in the raid. The militants had claimed to be holding 41.
Some hostages were freed, but the number of survivors was unconfirmed and officials in Britain said they were preparing for news of many British casualties, the BBC reports.
Al-Qaeda-linked fighters occupied the desert facility near the town of In Amenas, close to the Libyan border, on Wednesday, saying they had taken hostages in retaliation for French military intervention in neighbouring Mali.
During the Algerian military raid on Thursday as many as 600 Algerians and four foreign hostages - two from Scotland, one from France and one from Kenya - were freed, state news agency APS reported.
The Irish government has confirmed that one of its citizens, Stephen McFaul, escaped in the confusion when the army tried to stop the militants moving their captives in a convoy of about five vehicles.
Mr McFaul and other hostages were made to wear vests covered in plastic explosives as they were being moved, Mr Gilmore told CNN.
Five American hostages had survived and left the country, US officials told ABC News, while Japan said three of its nationals had been freed in the operation, but that 14 remained unaccounted for.
APS reported that the military, which had been surrounding the gas plant, targeted two vehicles as they tried to escape from the site with an unknown number of people on board. Militants told local media that Algerian forces had opened fire from the air.
Algerian Interior Minister Daho Ould Kablia said the kidnappers were Algerian and operating under orders from Mokhtar Belmokhtar, a senior commander of al-Qaeda in the Islamic Maghreb until late last year.
Communications Minister Mohamed Said Belaid said a "significant number of terrorists" were killed during the raid.
Countries question handling of raid
A spokesperson for British Prime Minister David Cameron said he was informed that the raid was under way when he called the Algerian Prime Minister, and made it clear that he would have preferred to have been told of this in advance.
Japan's government protested against the raid, urging Algeria "put the highest priority on people's lives". The United States said it was "seeking clarity" on what had happened.
Norwegian Prime Minister Jens Stoltenberg said he was told by his Algerian counterpart that the army "felt they had no choice but to go in".
The Tigantourine gas facility is about 40km south-west of In Amenas and about 1300km south-east of the capital Algiers.
BP operates the gas field jointly with Algerian state oil company Sonatrach and Norwegian firm Statoil.
