A militia group leader, who was convicted of the 2017 bombing of a mosque outside of Minneapolis that "terrorised" the community of Somali immigrants it served, was sentenced on Monday to 53 years in prison.

Emily Claire Hari, 50, was found guilty in December, after a five-week trial, on five federal charges related to the pipe bombing of the Dar al-Farooq Islamic Centre in Bloomington, Minnesota, while worshipers were in the building for morning prayers. No one was hurt in the bombing.

"Emily Claire Hari, 50, formerly known as Michael Hari, was sentenced to life in prison for the August 5, 2017, bombing of the Dar al-Farooq Islamic Centre in Bloomington, Minnesota", the US Department of Justice said in a statement.

In handing down the sentence on Monday, United States District Judge Donovan Frank described the attack orchestrated by Hari as a "highly sophisticated and premeditated act of domestic terrorism".

"Diversity is the strength of this country," Frank said. "Anyone who doesn't understand that doesn't understand the constitutional promise of this country that brings a lot of people here."

Hari and two accomplices, all from Clarence, Illinois, about 56 kilometres north of Champaign-Urbana, were arrested by FBI agents in March 2018.

All three were indicted the following June, but the other two, Michael McWhorter and Joe Morris, pleaded guilty to their roles in the bombing in January 2019.

Prosecutors had earlier described Hari as the ringleader who recruited the others into a militia group called "The White Rabbits" and drove a rented pickup truck more than 805km on Aug 4 and 5, 2017 to bomb the Islamic centre.

"Hari sought to terrorise an entire faith community. Today's sentence makes clear that such acts of hate-fuelled terror will not be tolerated," Deputy Attorney General Lisa Monaco said in a statement late on Monday.