US Intelligence officials say the number of Americans who have gone to Syria to join the extremist militants is rising “steadily”.
They estimate “dozens” of Americans have either gone to Syria or attempted to go to Syria to join the bloody insurgency.
The US has arrested some who have gone to Syria to fight alongside militants, but the estimate of “dozens” seems low enough that it raises questions if the US even knows how many are there, let alone is keeping tabs on them all.
Al-Qaeda-linked groups have been attracting thousands of people from across the region, Europe and Americas to go in Syria and fight in a conflict which started as pro-reform protests but now, as many believe, has turned to an all-out war against Syria.
A report by the American Pentapolis Agency of statistics in September showed the number of Arabs killed in the ranks of the so-called Free Syrian Army (FSA) was increasing and militants from 49 countries from the five continents of the world are fighting in Syria.
The report said there were at least 130 thousand non-Syrian militants in Syria, Arabs and non-Arabs.
A recent report showed at least four Britons have been killed in the past couple of months in Syria, fighting alongside al-Qaeda militants.
Many European officials have expressed concern about return of these militants to their countries.
Security experts fear that Britons who have travelled to fight in Syria – estimated by MI5 to number between 200 and 300 – may seek to radicalize others when they return to the UK.
Syria has been gripped by deadly unrest since 2011.
According to the United Nations, more than 100,000 people have been killed and millions displaced due to the turmoil that has gripped Syria for over two years.
The UN also says more than four million other Syrians will be forced out of their homes in 2014 by the escalating conflict in the country.
Two million Syrians are expected to take refuge outside the country while another 2.25 million are predicted to be internally displaced next year.