Authorities said the bloody takeover was carried out Wednesday by 32 men from six countries, under the command from afar of the one-eyed Algerian bandit Moktar Belmoktar, founder of the Masked Brigade, based in neighboring Mali. The attacking force called itself "Those Who Sign in Blood."

The militants initially said the operation was payback for French military intervention in neighboring Mali, where al-Qaida-linked rebels are on the march, but later they said it was two months in the planning, long before France sent in troops.

Armed with heavy machine guns, rocket launchers, missiles and grenades, the militants singled out foreign workers at the plant, killing some of them on the spot and attaching explosive belts to others.

Algeria's tough and uncompromising response to the crisis was typical of its take-no-prisoners approach in confronting terrorists, favoring military action over negotiation. Algerian military forces, backed by attack helicopters, launched two assaults on the plant, the first one on Thursday.

The militants had "decided to succeed in the operation as planned, to blow up the gas complex and kill all the hostages," Algerian Communications Minister Mohamed Said said in a state radio interview.

The Masked Brigade claimed responsibility for the attack in the name of al-Qaida, according to a video obtained by a Mauritania-based website that sometimes carries messages of jihadists.

An audio recording of Algerian security forces speaking with the head of the kidnappers, Abdel Rahman al-Nigiri, on the second day of the drama indicated the hostage-takers were trying to organize a prisoner swap.

"You see our demands are so easy, so easy if you want to negotiate with us," al-Nigiri said in the recording broadcast by Algerian television. "We want the prisoners you have, the comrades who were arrested and imprisoned 15 years ago. We want 100 of them."

In another phone call, al-Nigiri said that half the militants had been killed by the Algerian army on Thursday and that he was ready to blow up the remaining hostages if security forces attacked again.

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