French troops underestimated the strength of Islamist rebels when they launched a failed bid to free an intelligence officer held hostage in Somalia, the French defence minister said. One French soldier died and another went missing during the raid in which the hostage was probably killed by his captors, Defence Minister Jean-Yves Le Drian said on Saturday. He said 17 guerillas were killed. The overnight operation involving some 50 troops and at least five helicopters to free the intelligence agent, with the alias of Denis Allex, was launched by elite forces from the DGSE secret service, he said. "The resistance was stronger than expected and the heavy weaponry at the hands of the terrorists were clearly underestimated," said Le Drian. He said that one commando was dead and another missing and that "all indications" point to the fact that Allex had been killed by his captors belonging to al-Shabab, a Somali Islamist group affiliated to al-Qaeda. However, the group denied Allex was dead and said they were also holding the missing French commando. They also threatened reprisals against France. "In the end, it will be the French citizens who will inevitably taste the bitter consequences of their government's devil-may-care attitude towards hostages," an al-Shabab statement said. At least eight civilians were killed during the raid, witnesses said yesterday. A French expert involved in hostage negotiations said: "Talks with the Somali Islamists had become impossible due to the huge ransom demanded and the marked opposition of the Americans to the payment of ransom. "Denis Allex became a human shield and an operation had become indispensable."