Fourteen people in the United States - most of them US citizens - have been charged with providing support for al-Shabab in Somalia.
Al Shabab has close ties to Al Qaeda and was behind the bombing of a World Cup party in Uganda in which 74 people died.
The charges follow a two-year investigation by the FBI in Minnesota, Alabama and California.
Attorney General Eric Holder said it should send a strong message to anyone considering supporting al-Shabab.
The BBC reports the charges stem from four separate indictments in the states of Minnesota, Alabama and California.
Concerns about al-Shabab have grown after the group carried out a bomb attack in Uganda.
The indictments were unsealed on Thursday.