Mohamud Said Omar, 43, who is in custody in the Netherlands, is accused of being involved with many of the roughly 20 young men who left Minneapolis in waves from December 2007 through November 2008.

Omar is among 14 charged in the investigation some terrorism experts call one of the largest of its kind.

"The numbers are huge compared to other domestic terrorism cases that have been brought," said Michael Greenberger, director of the University of Maryland Center for Health and Homeland Security.

Several individuals are accused in court documents of a mix of recruiting and raising funds for travel, and of engaging in terrorist acts in Somalia. Some allegedly attended training camps run by the Islamists, which the U.S. says has ties to al-Qaida. All but one of the men who left the Minneapolis area are of Somali descent.

"We haven't seen anything like that before in the United States," Ralph S. Boelter, the special agent in charge of the FBI's Minneapolis field office, said of the case. "The recruitment is a global problem. ... It varies in intensity from place to place. I think (Minneapolis) is the center of it."

An affidavit unsealed Tuesday alleges the young Somalis' departures began with six men leaving in December 2007. Another left the following February, two more that August and another six last November.

The affidavit by Assistant U.S. Attorney W. Anders Folk states that before the first group left in 2007, Omar gave travel money to some "members of the conspiracy."

Omar returned to the U.S. that April and was stopped by U.S. Customs and Border Protection in Atlanta because he had an expired Minnesota driver's license, purchased his airline ticket with cash and was returning from a three-month trip to Somalia, according to another FBI affidavit.

Source: (AP)