Europe and the United States are drawing up a new wave of anti-terror measures to try to stop the growing number of would-be jihadists from going to fight in Syria and Iraq.
France unveiled a new bill on Wednesday to ban foreign travel for those suspected of being radicalised, after US Attorney General Eric Holder claimed that returning fighters pose a "grave threat".
Nine EU interior ministers met in Milan on Tuesday to put together a plan of action to identify young people who have signed up to fight with Islamist groups against the Syrian regime of President Bashar al-Assad.
"Recent developments in Iraq increase the need to act immediately," EU counter-terrorism coordinator Gilles de Kerchove said.
He said the declaration of a "caliphate" by the feared Sunni militants of the Islamic State in areas they control in Iraq and Syria was likely to prove a potent attraction for would-be European jihadists.
But as calls grow for tougher action, Britain's former intelligence chief has warned that the clamour could backfire on the West.
The United States and its European allies have been working on greater cooperation, with Holder using a visit to Norway on Tuesday -- which has one of the highest rates of nationals per capita fighting in Syria -- to call for a coordinated clampdown.
"We cannot afford to be passive," he told journalists.
"The Syrian conflict has turned that region into a cradle of violent extremism. But the world cannot simply sit back and let it become a training ground from which our nationals can return and launch attacks. And we will not."
- 'Problem for all' -
US intelligence official estimate that of the 7,000 foreign fighters in Syria only around a dozen are Americans. But as many as 2,000 Europeans are thought to be engaged in the fighting, 800 alone from France, including several women.
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Holder said the ability of European and American citizens to travel visa-free between their two continents meant that "the problem of fighters in Syria returning to any of our countries is a problem for all of our countries".
But Sir Richard Dearlove, who was head of Britain foreign intelligence during the war in Iraq, claimed that governments and the media have blown the Islamist threat out of proportion, which could prove counter-productive.
In an address to a defence think-tank in London on Monday, he said the West was not the main target of radical fundamentalism groups such as ISIL, which now calls itself the Islamic State since overrunning much of northern Iraq from its strongholds in Syria.
The ex-MI6 chief claimed that the conflict in Syria was "essentially one of Muslim on Muslim".
He warned that giving the "oxygen of publicity" to jihad tourism was counter-productive. He said the media were making monsters of "misguided young men, rather pathetic figures" who were getting coverage "more than their wildest dreams".
"It is surely better to ignore them," he added.
The French government, however, is deeply concerned about the radicalisation of its nationals who have gone to fight in Syria.
Those fears were heightened by the arrest of Frenchman Medhi Nemmouche, who spent a year in Syria, after the shooting at the Brussels Jewish Museum in May that left four people dead.
A Tunisian accused of recruiting young jihadists to fight in Syria has since been deported, while 26-year-old Ibrahim Ouattara was jailed for four years by a Paris court on Wednesday for trying to join Islamist rebels in northern Mali.
The new French bill gives the authorities the power to slap a ban on foreign travel on anyone suspected of being radicalised, and temporarily confiscate and invalidate their passports.
Airlines will be banned from carrying targeted passengers and will have to notify French authorities the moment one of them makes a reservation.
A Passenger Name Record -- containing the itinerary for a certain passenger or group in computer reservation systems -- will be given to European authorities to help identify such people.
If the people targeted under the ban do manage to go abroad, they will be the subject of an international arrest warrant.
Dearlove urged caution, however, saying governments should move away from the "distortion" of the post-9/11 mindset to to make "realistic risk assessments", and to think rationally about the causes of the crisis in the Middle East.