Church murders 'act of domestic terrorism' say US police

Photographs of the nine victims killed at the Emanuel African Methodist Episcopal Church in Charleston, South Carolina. Photo / Getty Images

Federal authorities are investigating the murder of nine black churchgoers as a possible hate crime and an "act of domestic terrorism," the Department of Justice says.

State authorities in South Carolina have already charged 21-year-old suspected white supremacist Dylann Roof with nine counts of murder, and the federal investigation is running in parallel.

"This heartbreaking episode was undoubtedly designed to strike fear and terror into this community," Department of Justice spokeswoman Emily Pierce said on Friday.

A woman weeps outside the historic Emanuel African Methodist Episcopal Church, June 19, 2015 in Charleston, South Carolina. Photo / Getty Images

"And the department is looking at this crime from all angles, including as a hate crime and as an act of domestic terrorism."

Roof has reportedly confirmed to investigators that he carried out Wednesday night's attack on a Bible study group meeting in a historic black church in downtown Charleston, South Carolina.

Witnesses have reportedly said that he harboured racist views and was seeking to trigger a race war in the United States, but it is not known whether he is a member of an extremist group.

- AAP