France insisted Monday it was not spooked by a call for Muslims to kill citizens of countries fighting the Islamic State group, hours before jihadists claimed the kidnapping of a Frenchman in Algeria.
An image released by jihadist outlet al-Itisam Media on June 29, 2014, is said to shows Islamic State members including Abu Mohammed al-Adnani (right), whose picture was blurred by the source to protect his identity, speaking at an unknown location
"France is not afraid," Interior Minister Bernard Cazeneuve said repeatedly during a televised statement, after IS circulated grisly tips for its followers on how to kill "disbelievers".
The Algerian group Jund al-Khilifa, which has pledged allegiance to IS, said in a video that they would kill French national Herve Pierre Gourdel, who was abducted in a mountainous region of northeastern Algeria on Sunday, unless Paris halts air strikes on the extremists in Iraq.
In the video, the kidnappers said they were responding to the IS appeal to kill citizens of countries who have joined the coalition against them.
French President Francois Hollande spoke with Algerian Prime Minister Abdelmalek Sellal on Monday and said both countries were working together to free the Frenchman.
Earlier Cazeneuve had defied an explicit threat against what IS labelled "the spiteful and filthy French", saying it was "not the first time France has been threatened by terrorist groups".
Paris did however urge nationals abroad to exercise "utmost caution" after the threat.
- Rewriting anti-terror laws -
The menace posed by the slick, web-savvy Islamic State group that has seized large areas of Iraq and Syria has seen anti-terror laws rewritten, security boosted and raids carried out against homegrown jihadist groups from Europe to Australia.
Authorities are fearful that returning jihadists will launch attacks at home, like French citizen Mehdi Nemmouche, who is suspected of killing four people in an attack on the Jewish Museum in Brussels in May.
France has Europe's largest Muslim population, and 930 of its citizens have joined the fighting in Syria and Iraq, according to official figures.
French deputies voted last week on a new counter terrorism law aimed at halting the flow of would-be jihadis to the war-torn region.
"The question on everyone's lips is not when there will be an attack, but where," said a French intelligence source.
The UN Security Council will on Wednesday discuss a resolution that would oblige nations to prosecute those who travel to fight with jihadist groups or fund them.
President Barack Obama will preside over the efforts to boost international cooperation in the fight against IS, which has seen the US and France carry out air strikes against the group.
Australia is also deploying fighter jets to join the campaign.
Meanwhile the United Kingdom and Australia were drawing up tougher laws of their own. Britain, which has raised its terror risk level to "severe", is planning measures that will allow police to temporarily strip departing suspects of passports at the border.
Erin Marie Saltman, a senior researcher at the London-based Quilliam think-tank, said the call by IS for individuals to kill "disbelievers" could "shake" counter-terrorism efforts.
"It is very hard to track down these individuals... threat levels will remain high for the foreseeable future throughout Europe," said Saltman.
She highlighted the recent case in Australia where authorities last week foiled a plot by IS jihadists to carry out gruesome "demonstration executions" of random civilians.
- 'Lone wolves' -
France, which is home to Europe's largest Muslim population, said security forces were "fully mobilised" to deal with any threat at home.
"This is not the first time France has been threatened by terrorist groups who attack the values of tolerance... respect for human rights and democracy, which France has upheld through its secular history," Cazeneuve said.
"Even if there is no such thing as zero risk, today we are taking 100 percent precautions."
Security has also been stepped up at the Brussels headquarters of the European Union after a Turkish man and woman who had recently spent time in Syria were arrested under anti-terrorism laws.
Anne Giudicelli, of the anti-terror consultancy Terr(o)risc, said IS threats were part of "a psychological war... that works very well".
But she warned that official statements reacting to the threats "can tend to give them (IS) legitimacy in the eyes of some people".
Steven Emerson of the US-based Investigative Project on Terrorism said the call by IS was nothing new.
"This was an expected development, already in the making, as they had brazenly executed American citizens in an effort to provoke the United States into attacking it," he told AFP.
"I think in the end it may provoke 'lone wolves' and returning jihadi veterans to strike but they already had the motivation and impetus to do so already," he told AFP.