Islamic militants claimed that 35 hostages and 15 militants were killed after Algerian military helicopters strafed the area but said seven hostages survived.

Islamists with the Masked Brigade, who have been speaking through a Mauritanian news outlet, said the Algerians opened fire as the militants tried to leave the vast Ain Amenas energy complex with their hostages a day after seizing the installation deep in the desert.

Algerian forces had surrounded the complex in a tense standoff since the plant was seized early Wednesday and had vowed not to negotiate with the kidnappers, who reportedly were seeking safe passage.