Promising both "true brotherhood" and "fun," several Somali men convinced fellow immigrants in Minneapolis to return to their East African homeland and take up arms with a terrorist group, according to federal charges unsealed Monday against eight individuals.

The charges are part of an unfolding federal investigation into the disappearance of as many as 20 young Somali men from Minneapolis over the last two years _ most of them U.S. citizens who federal authorities say are guilty of terrorism. Federal prosecutors say most of the men traveled to Somalia to join the terror group al-Shabab, which the U.S. State Department says has links to al-Qaeda.

Ralph S. Boelter, the special agent in charge of the FBI's Minneapolis field office, called the latest round of indictments a "tipping point" in the more than yearlong investigation. "We have reached momentum, and reached a point where we will have full resolution of this case," Boelter said at a news conference with Minnesota's U.S. Attorney, B. Todd Jones.

Fourteen people have been charged in the investigation. The eight charged Monday are accused of a mix of recruiting and raising funds for the trips, and of engaging in terrorist acts in civil war-torn Somalia. Indictments say some attended terrorist training camps where they received instruction in firing small arms and machine guns, military style tactics and indoctrination in "anti-Ethiopian, anti-American, anti-Israel, and anti-Western beliefs," according to a federal affidavit.

Two of those charged Monday helped raise money for the trips by approaching unknowing members of Minnesota's Somali community and soliciting funds by telling them it was to pay for trips for young Somali men to travel to Saudi Arabia and study the Koran, according to the affidavit.

Boelter and Jones said one reason they disclosed new details about the case was to reassure members of Minnesota's Somali community that the investigation is focused on a relatively small group of individuals. The larger community "has consistently expressed deep concern about this pattern of recruitment activity," Jones said.

Still, the federal officials declined to say whether any of the new indictments targeted alleged leaders or masterminds of the recruitment scheme. The investigation is ongoing, they said, and there could be more indictments and arrests. Federal officials declined to name a local mosque which court documents allege was a site for some recruiting and planning.

Of the 14 people indicted, four have pleaded guilty and are awaiting sentencing. Seven are not in custody and are believed to be outside the United States.

Boelter said he did not think that Minnesota Somalis are still being recruited, but he could not say for sure. "I'm confident it's not happening, but you're never 100 percent sure there's no activity," he said.

FBI Director Robert Mueller has said the case is worrisome because it shows young men raised in the United States can be recruited by terrorists overseas, trained to conduct attacks and in some cases killed in the fighting there.

One of the men who left Minneapolis, Shirwa Ahmed, allegedly carried out a suicide bombing in Somalia's Puntland region in October 2008. New charges unsealed Monday said Ahmed was also among a group of al-Shabab fighters who launched an armed ambush against Ethiopian troops.

Boelter said he had "no indication" that any of the Somali men ever intended to engage in a terrorist attack in the United States. "But the national security implications are evident _ Americans with U.S. passports attending foreign terror camps," he said.

One of the eight named Monday was Mohamud Said Omar, who was arrested earlier this month in the Netherlands. Prosecutors accused Omar, a Somali citizen and U.S. permanent resident, of helping with travel plans for some men between Minneapolis and Somalia, and providing hundreds of dollars to fund the purchase of AK-47 rifles for the men.

Two of Omar's brothers who live in Minnesota have said they believe their sibling is innocent, was not an extremist and was so poor that he couldn't afford to bring his new wife from Somalia to the U.S.

The newly unsealed court documents reveal a series of meetings beginning in 2007 "in a variety of locations around the Twin Cities," as well as in phone calls in which several individuals, both in Somalia and in Minnesota, tried to convince Minnesota Somalis of the worthiness of the cause.

Somalia has not had a functioning government since 1991, when warlords overthrew a socialist dictator and then turned on each other, causing chaos in the African nation of 7 million. Minnesota has the largest population of Somali immigrants of any U.S. state.

The investigation, which Boelter described as "global" in scope, has spread beyond Minnesota to California, Ohio, Massachusetts and multiple foreign countries.

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Associated Press writer Devlin Barrett in Washington contributed to this report.