In testimony before the Senate Committee on Homeland Security and Governmental Affairs, US counterterrorism chief Nick Rasmussen said IS had overtaken al Qaeda as leader among global violent extremist movements and that the organization had access to a large pool of potential recruits in Western countries. The organization has been known to take to social media to attract further recruits.

He added counterterrorism experts still regarded the Yemen-based al-Qaeda in the Arabian Peninsula (AQAP) also as a big threat due to its interest in attacking the United States and airplanes.

US aware of many extremist threats

Also giving testimony before the committee, FBI Director James Comey said US investigators were aware of many US-based Islamic militant suspects.

Comey said investigators had followed "dozens and dozens of people around the United States 24/7" during the summer and had managed to "disrupt" them. Comey added that Islamic State recruits from the United States were becoming younger with more women and girls seeking to join the militant group. He also highlighted that the militants were now using encrypted communications to escape detection.

Refugees and security threats

Comey said the US government had improved its methods in screening refugees from foreign countries to ensure they would not pose terrorism threats or other risks to the United States, but he added that there always were risks associated with welcoming migrants from a country experiencing strife. Still, Comey said, the United States had "developed an effective way to touch all our databases" and gather information about the individuals.

US President Barack Obama's administration announced last month that it would increase the number of worldwide migrants it intended to take in over the next two years. That number would include many refugees from war-torn Syria, where the self-declared "Islamic State" (IS) militant group has claimed roughly half of the country's territory.

ss/sms (AP, Reuters)