US says it is probing Charleston church murders as 'domestic terrorism'

Federal authorities are investigating the murder of nine African-American churchgoers as a possible hate crime and an "act of domestic terrorism," the Department of Justice said Friday.

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 spokesperson Emily Pierce said.

"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 harbored 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.