Around half of homegrown European militants are French nationals, according to a report prepared by the French Senate, the upper house of parliament, on Wednesday. Forty-seven percent of French militants, at least 1,430 people, have fled to the conflict zones in Iraq and Syria. Europe's police organization, Europol underscored that roughly 5,000 radicalized European fighters in Syria will continue to pose a greater risk to European countries as they become more hostile to the West. France has witnessed the largest number of youths leaving to join the Islamic State of Iraq and al-Sham (ISIS).

The report, prepared by Senator Jean-Pierre Sueur, found the number of French nationals involved in ISIS networks has increased by 24 percent since November 2014. More than 3,000 French nationals suspected of having links with ISIS militants have been under scrutiny by French domestic intelligence services.

The report said that there are some 200 radicalized French militants who have returned to France from the Middle East. In the face of a large number of homegrown militants posing an extremist threat, France is also preparing an extensive de-radicalization program for returning militants to be applied in French prisons. However, the new measures have stirred growing criticism for possibly promoting a perfect environment for easily radicalizing Muslim prisoners. Ever since the rise of ISIS, France has been increasingly anxious about becoming an ISIS-recruiting hub.

The first French citizen was convicted of joining an overseas radical group in November 2014 and was given a seven-year prison sentence. The report says that since then, 152 French radicals have been held in prison.

A large number of male French nationals have looked to travel to Iraq and Syria to fight alongside ISIS. The two perpetrators of the Charlie Hebdo massacre on Jan. 7, Cherif and Said Kouachi, are also homegrown militants who made connections with al-Qaida in the Arabian Peninsula (AQAP). They were French nationals born to Algerian parents and were raised in France.

The Charlie Hebdo massacre showed that the most serious terrorist threat Europe faces does not comes from the Middle East or West Africa, but from EU nationals who support ISIS or al-Qaida. While reassessing the terrorist threat to Europe, it has been acknowledged that homegrown militants have become the major threat for European countries. The security threat posed by ISIS-linked homegrown militants has recently drawn much more attention in Europe. An estimated 450 young people from Belgium, a small European country with a population of just 11 million, have joined ISIS. The number of individuals traveling from Denmark to conflict zones in Syria and Iraq has reached at least 110. More than 500 British nationals are believed to have travelled overseas to join ISIS, according to figures released in August 2014. The number is expected to rise as more Britons have sought to join the radical group.