ALGIERS, Algeria (AP) -- 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 militant spokesman said the kidnappers were attacked by Algerian helicopters when they attempted to leave the complex.

The Algerian government would not immediately comment on the standoff and the Associated Press was not able to independently confirm the information.

Earlier in the morning, a group of 20 hostages was reported to have escaped their captors. That report came from an Algerian security official. The official said those escaping included Americans and Europeans. He did not give any further details.

The official spoke on condition of anonymity because he was not authorized to speak to the press.

The gas plant has been surrounded by the Algerian army and there's now a tense standoff with the militants.