PARIS, Jan. 12 (Xinhua) -- French president on Saturday expressed great distress over the French victims killed in the hostage rescue operation in Somalia, but vowed not to give up to terrorists' blackmail.
In the weekend televised address, President Francois Hollande confirmed that "this operation could not be completed despite the sacrifice of our two soldiers and probably the murder of our hostage."
Hollande said the decision to "free one of our agents detained for more than three and a half years in harsh conditions" had been made for several days.
The French head of state said he shared the pain of their families and presented to them "the condolences of the nation," stressing that "this operation confirms France's determination not to give in to blackmail by terrorists."
France launched a hostage rescue operation on early Saturday morning, trying to free Denis Allex, a secret agent abducted in Somalia since 2009.
"Last night, the commando of the DGSE ... faced strong resistance. Fights of great violence took place during which, evidence suggests that Denis Allex was killed by his captors," Defense Minister Jean-Yves Le Drian told a press briefing.
Two French soldiers and 17 militants from al-Qaeda linked al-Shabab group were also reportedly killed in the raid.
However, the Islamist group denied Alex's death and to judge him in the coming two days, adding they detained an injured French soldier.
Abducted in 2009 by al-Shabab insurgents in Mogadishu, Allex was alleged to have helped train Somalia's police and presidential guards along with another agent who succeeded to escape a month later.
France's hostage rescue operation came just a day after France sent its forces to help Malian authorities push back the Islamist rebels' offensive and movement toward the capital of Bamako.
"There is new situation with a break in the process and the advance of Islamist forces to the south of Mali will reinforce the weight of these movements and directly harm the hostages' lives," the minister noted.
In September, AQIM menaced in an online message to kill the remained four French workers of Areva kidnapped in 2010, if Paris would prepare a military intervention alongside African forces to oust Islamist insurgents from northern areas of Mali.
Le Drian stressed that French hostage taking will not constitute a pressure on Paris "to fight against terrorism where it is."
"Our commitment to fight against the terrorists and who threat to set a terrorist state in Mali will continue. We are determined to set up the conditions allowing the establishment of the Security Council strategy," the French official said.
"We will continue our efforts to obtain the release of all hostages," he added.
Meanwhile, Jihadists warned that France's military intervention against them in northern Mali will put "not only for French hostages, but also for all French citizens wherever they find themselves in the Muslim world" at risk, as French forces carried out air strikes for the second day on Saturday against Islamist rebels in Mali.
In the evening, President Hollande announced in a television address after a defense council meeting that France will raise anti-terror alert level to the highest level on fears of post-Mali operation reprisals.
In accordance with the president's instructions, French Prime Minister Jean-Marc Ayrault announced that the terror alert Vigipirate plan was reinforced "immediately" for public transport, rallies and public buildings.
"The government is mobilized and remains attentive to the evolution of the situation. (It) shall take all necessary decisions to ensure national security," said the PM office.
The Vigipirate plan was implemented in Match 2003. The alert "scarlet" was briefly imposed in March 2012 in France's Midi-Pyrenees region at the time of the killings by Mohamed Merah in Toulouse and Montauban.
Eight French nationals are still being held hostage by Islamist groups in the Sahel region.