A US jury on Thursday found avowed white supremacist Dylann Roof guilty of federal hate crimes resulting in the deaths of nine black parishioners at a historic church in Charleston, South Carolina, last year.

Jurors also said Roof, 22, was guilty of firearms violations and obstructing the exercise of religion for those he shot and killed during a Bible study at Emanuel African Methodist Episcopal Church on June 17, 2015.

The 12 jurors deliberated for a little less than two hours. Roof showed no emotion as the verdicts were read.

The guilty verdicts on all 33 charges paves the way for the penalty phase of Roof's trial, which is set to begin on January 3.

He has indicated he will serve as his own lawyer as prosecutors pursue a death sentence.

The jury rendered its verdict after hearing six days of testimony in Charleston, a city on edge in recent weeks as two racially charged trials played out in courthouses across the road from each other.

A state murder trial against a former North Charleston police officer who shot and killed a black man fleeing a traffic stop last year ended on December 5 in a mistrial.

Whether Roof carried out the mass shooting that intensified the debate about race relations in the United States was not in dispute.

But his defence lawyers, hoping to spare him from execution, asked jurors to consider what factors had driven Roof to commit the senseless act and suggested he might be delusional.

The defence did not call any witnesses after the judge blocked them from presenting evidence of Roof's mental state during the guilt phase of the trial.

During closing arguments on Thursday, prosecutors dismissed the defence's position and said Roof's guilt had been proved "beyond any doubt, much less reasonable doubt."

"He must be held accountable for each and every action he took inside that church," Assistant US Attorney Nathan Williams said. "For every life he took."