Islamic State ISIS
French jihadists depicted in Raqqa talking of the Charlie Hebdo attackAl-Hayat Media

More than 6,000 European could be fighting with jihadist groups in Syria, according to a top EU official.

"At the European level, we estimate that 5,000-6,000 individuals have left for Syria," EU Justice Commissioner Vera Jouriva told Le Figaro in an interview, adding that more than 1,500 French nationals could be waging jihad in the embattled country.

However, this number could be far higher due to the difficulty of tracking foreign fighters in the conflict, the commissioner added.

"At the time of the attacks in Paris and Copenhagen, we decided not to allow ourselves to be guided by fear," she said, referring to January's twin Islamist attacks in the French capital and the subsequent deadly shootings in a cultural centre in Denmark.

French child killed Syria Isis
A 13-year-old boy from France was reportedly killed while fighting for the Islamic State (Isis) in SyriaTwitter/@_DavidThomson

Jouriva said that focusing on those seeking to leave for Syria to wage jihad, or those returning from the conflict, was intervening "too late".

She said that instead the EU wanted to curtail the steady flow of Europeans to the area by looking at the diverse reasons of why people joined jihadist groups beyond simply religion.

Information sharing required

According to British research, "a desire for adventure, boredom, dissatisfaction with their situation in life or a lack of prospects" were some of the reasons given by those who had opted to head for Syria.

Another focus for the EU was speeding up the exchange of information between the police forces and court systems of member states, Jouriva said, adding that more intelligence sharing is required.

More than 215,000 people have been killed in Syria's four-year war, which is increasingly dominated by jihadist groups.