Israeli security is confirming that it denied entry to three North Carolina men accused of plotting to execute terror attacks in foreign countries.

U.S. authorities arrested Daniel Boyd and his two sons Monday, along with six other men. They allege Boyd was the ringleader of a group gearing up for violent jihad. The indictment said Boyd and his sons traveled to Israel in 2007 to meet with two of the other defendants but were denied entry and detained for two days.
   
Attorney General Eric Holder told ABC News that he is troubled by the new, emerging threat of Americans training with terrorists overseas and returning home.  

"The whole notion of radicalization is something that didn't loom as large a few months ago as it does now," Holder said. "And that's the shifting nature of threats that keeps you up at night."
   
Authorities believe Boyd trained in terrorist camps overseas. A detention hearing for the seven suspects is set for August 4.