The EU counter-terrorism chief, Gilles de Kerchove, told AFP on Tuesday that ISIS, also known as the Islamic State, has seen a massive surge in fighters from Europe joining the terror network as it takes over huge swathes of territory in Syria and Iraq with the aim of establishing a "Caliphate" state.
According to de Kerchove, at least 10 percent of all ISIS militants were either born in Europe or lived there for extended periods, as the group's numbers swelled from 2,000 to 3,000 over the past few months.
The anti-terror chief said that social media has played an integral part in recruiting young Muslim men from Europe, and has been very successful due to numerous Facebook and Twitter campaigns.
"My own assessment is that we're about 3,000, The flow has not been dried up and therefore possibly the proclamation of the caliphate has had some impact," he said.
As there are an estimated total of 30,000 ISIS militants in the Middle East, if 3,000 of those are from Europe, that does indeed constitute a tenth of the whole fighting force.
De Kerchove said it's well-known that many ISIS recruits come from France, Britain, Germany, Belgium, The Netherlands, Sweden, and Denmark. He also confirmed that the group has recently seen an expanding growth from Spain, Italy, Ireland, and Austria.
"Even a country like Austria I think has now foreign fighters, which I was not aware of before," he said.
With the backdrop of an increasingly menacing enemy in ISIS, President Obama's administration has been gathering together a coalition of western and Arab states, which has begun a campaign of airstrikes against the group in Iraq and now in Syria.
As well as the threat posed to Europeans, Australia had also been subjected to the Islamic State's wrath, with one cell recently arrested ahead of carrying out plans to behead a random member of the public. A local terrorist was also shot dead after stabbing two police officers.
The dangerous and growing threat to European citizens at the hands of ISIS is now obvious, but has the response been too little too late?