An Algerian security official said de-mining squads searching for explosives have found “numerous” bodies at a gas refinery where Islamic militants took dozens of foreign workers hostage.

The official said the bodies were difficult to identify and it was impossible to determine if they were foreign hostages or others.

Algerian special forces stormed the natural gas complex in the Sahara desert yesterday to end the stand-off, and the government said all 32 militants were killed.

Earlier yesterday, Algeria’s chief government spokesman said he feared the toll of hostages – which stood at 23 – would rise as the special forces teams finished their search.

Officials said the militants came from six countries and were armed to cause maximum destruction. Sonatrach, the Algerian state oil company running the Ain Amenas site along with BP and Norway’s Statoil, said the entire refinery had been mined.

“They had decided to succeed in the operation as planned, to blow up the gas complex and kill all the hostages,” said communications minister Mohamed Said, speaking on a state radio interview.

The American government had warned that there were credible threats of more kidnapping attempts on Westerners.

With few details emerging from the remote site in eastern Algeria, it was unclear whether anyone was rescued in the final operation, but the number of hostages killed on Saturday – seven – was how many the militants had said that morning they still had.

The siege at In Amenas transfixed the world after radical Islamists linked to al-Qaida stormed the complex on Wednesday, which contained hundreds of plant workers from all over the world.

They held them hostage surrounded by the Algerian military and its attack helicopters for four tense days that were punctuated with gun battles and dramatic tales of escape.

Algeria’s response to the crisis was typical of its history in confronting terrorists, favouring military action over negotiation, which caused an international outcry from countries worried about their citizens.

Algerian military forces twice assaulted the two areas where the hostages were being held with minimal apparent mediation – first on Thursday, then on Saturday.

“To avoid a bloody turn of events in response to the extreme danger of the situation, the army’s special forces launched an intervention with efficiency and professionalism to neutralise the terrorist groups that were first trying to flee with the hostages and then blow up the gas facilities,” Algeria’s Interior Ministry said in a statement.

De-mining teams began going through the complex today, searching for explosive traps left behind by the militants, the state news service said. Sonatrach, the Algerian state oil company running the In Amenas site along with BP and Norway’s Statoil, said the entire refinery had been mined. The State Department issued a travel warning last night for Americans in or travelling to Algeria, citing credible threats of the kidnapping of Western nationals. The department also authorised the departure from Algeria of staff members’ families if they choose to leave.

Immediately after the assault, French president Francois Hollande gave his backing to Algeria’s tough tactics, saying they were “the most adapted response to the crisis”.

“There could be no negotiations” with terrorists, the French media quoted him as saying in the central French city of Tulle.

Mr Hollande said the hostages were “shamefully murdered” by their captors, and he linked the event to France’s military operation against al-Qaida-backed rebels in neighbouring Mali. “If there was any need to justify our action against terrorism, we would have here, again, an additional argument,” he said.

In the final assault, the remaining band of militants killed seven hostages before 11 of them were in turn cut down by the special forces, Algeria’s state news agency said.

The military launched yesterday’s assault to prevent a fire started by the extremists from engulfing the complex and blowing it up, the report added.

A total of 685 Algerian and 107 foreigner workers were freed over the course of the four-day stand-off, the Interior Ministry statement said, adding that the group of militants that attacked the remote Saharan natural gas complex consisted of 32 men of various nationalities, including three Algerians and explosives experts.

The military also said it confiscated heavy machine guns, rocket launchers, missiles and grenades attached to suicide belts.

Algeria has fought its own Islamist rebellion since the 1990s, elements of which later declared allegiance to al-Qaida and then set up new groups in the poorly patrolled wastes of the Sahara along the borders of Niger, Mali, Algeria and Libya, where they flourished.

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