US federal prosecutors will seek the death penalty for Dylan Roof, the 22-year white male accused of killing nine black church-goers in Charleston, South Carolina, last June, the US Justice Department said on Tuesday.

"Following the department's rigorous review process to thoroughly consider all relevant factual and legal issues, I have determined that the Justice Department will seek the death penalty. The nature of the alleged crime and the resulting harm compelled this decision,” US Attorney General Loretta Lynch said in a statement.

Roof faces 33 federal charges, including hate crimes, for shooting the parishioners during a Bible study session at the historic Emanuel African Methodist Episcopal Church in Charleston.

Prosecutors claim the crime was motivated by white supremacist views.

He also faces the state death penalty if convicted of the shootings.

Roof's defense attorneys had said he would plead guilty if he did not face the death penalty.

cw/rc (dpa, Reuters)