Two Somalia-born US citizens living in Minnesota were accused of raising money and sending it to Al-Shabab and lying to FBI investigators, according to one indictment unsealed in a Minnesota court.

Amina Farah Ali and Hawo Mohamed Hassan were charged in a 16-count indictment that detailed their efforts to raise money for Al-Shabab by going door-to-door in the Somali communities in Minnesota and elsewhere in the United States and Canada, the indictment said.

They also held teleconferences to raise funds, sometimes saying it would be used to help the poor and needy in Somalia.

Ali was accused of sending about $8,600 to Al-Shabab, according to the indictment.

US prosecutors also unsealed a three-count indictment from 2009 that charged a young man, Omar Shafik Hammami, who grew up in Alabama but left for Somalia, with providing material support and resources to al Shabaab.

It was not immediately clear whether any of the three individuals were in US custody. An FBI spokesman declined comment.

The Obama administration has been increasingly concerned about al Shabaab, particularly after the group successfully carried out a suicide bombing attack in Uganda killing more than 70 people, including one American.

That was the first successful strike by the group outside Somalia. US intelligence agencies have warned of growing links between Al-Shabab in the partially lawless country and Al-Qaeda's network in East Africa.

The unsealing of the indictments follows the arrest of two other American men in the last few weeks in separate cases on charges they were trying to travel to Somalia to aid Al-Shabab. One was arrested in Virginia and another in Chicago before they could leave for Africa.