Federal authorities yesterday unsealed terrorism-related charges against eight men, accusing them of recruiting at least 20 young Somali Americans from Minnesota to join an extremist Islamic insurgency in Somalia.

The newly named suspects make up one of the largest suspected terrorist networks in the United States since the Sept. 11, 2001, attacks, analysts said. Assistant Attorney General David Kris said the government continues to investigate the alleged recruitment, and sources indicated that FBI and grand jury inquiries are active in San Diego, Boston and Columbus, Ohio, into the disappearance abroad of dozens of Muslim Americans since 2007.

The charges cap a year-long FBI investigation into the departures, most of them among men of Somali descent in their teens and 20s, to join al-Shabaab, an extremist group with ties to al-Qaida.

Al-Shabaab opposes Somalia's weak but internationally supported government and seeks instead a fundamentalist Islamic state under sharia law. It has since attacked Ethiopian and African Union troops, targeted neighboring countries, pledged allegiance to al-Qaida leader Osama bin Laden last year and used al-Qaida operatives to train American recruits, U.S. officials said. The State Department listed al-Shabaab as a terrorist group last year.

U.S. officials said they worry that al-Qaida operatives might "commission" a U.S. strike using al-Shabaab's pipeline of American and European fighters, whose passports would make it easier for them to travel undetected, although they have said they see no sign yet of such a threat.

Among those charged yesterday was Mahamud Said Omar, a U.S. permanent resident arrested two weeks ago in the Netherlands. Mr. Omar paid for airfare and AK-47 rifles for several of the youths to join al-Shabaab, officials said yesterday at a news conference in Minneapolis. U.S. officials requested the arrest and seek his extradition.

Officials also announced charges against seven other men, all outside the United States and not in custody. They include Cabdulaahi Ahmed Faarax and Abdiweli Yassin Isse, who were formally charged Oct. 9, one day after they told a U.S. border agent that they were headed from San Diego for Tijuana, Mexico.

According to an FBI affidavit, Mr. Faarax and Mr. Isse conspired to recruit and pay for six Somali American youths to go abroad in December 2007, including Shirwa Ahmed, 27, a college student from Minneapolis. He blew himself up in one of five simultaneous attacks that killed 22 U.N. aid workers and others in Somalia in October 2008, Special Agent Michael Cannizzaro wrote in the affidavit.

The group included several cooperating witnesses among six other Somali Americans who pleaded guilty on related charges this year, according to court documents.

Mr. Faarax told the group "that he experienced true brotherhood while fighting in Somalia and that travel for jihad was the best thing that they could do," the agent wrote. He said Mr. Faarax told the young men that they would get to shoot guns, and that "traveling to Somalia to fight jihad will be fun, and not to be afraid."

Also charged with conspiracy to support terrorism and to kill outside the United States were Ahmed Ali Omar, Khalid Mohamud Abshir, Zakaria Maruf, Mohamed Abdullahi Hassan and Mustafa Ali Salat, according to grand jury indictments unsealed. The men -- all U.S. permanent residents who left for Somalia between December 2007 and August 2008 -- were also charged with firearms charges and solicitation to commit violent crime.

Georgetown University terrorism analyst Bruce Hoffman noted that the charging documents mention only recruits from Minneapolis, and refer only glancingly to al-Shabaab's links to al-Qaida.

The documents unsealed yesterday say the group that left Minnesota in December 2007 purportedly went to training camps in southern Somalia, where they met dozens of other Somali youths from the United States and other countries. They received military-style training in using machine guns and rocket-propelled grenades from Somali, Arab and Western instructors, the documents state.

U.S. officials this fall said one key trainer included Saleh Ali Nabhan, 30, a liaison to al-Qaida in Pakistan who was wanted for his role in the 1998 attacks on two U.S. embassies in Africa. He was killed in a U.S. helicopter raid Sept. 14. In the documents released yesterday, U.S. officials said recruits were purportedly "indoctrinated with anti-Ethiopian, anti-American, anti-Israeli and anti-Western beliefs."

"The sole focus of our efforts in this matter has been the criminal conduct of a small number of mainly Somali American individuals, and not the broader Somali American community itself, which has consistently expressed deep concern about this pattern of recruitment activity in support of al-Shabaab," said Ralph Boelter, special agent in charge of the FBI's Minneapolis field office.

Washington correspondent Daniel Malloy writes the "Pittsburgh On The Potomac" blog exclusively at PG+, a members-only web site of the Pittsburgh Post-Gazette. Our introduction to PG+ gives you all the details.