WASHINGTON (AFP) - A US federal grand jury on Wednesday indicted suspected white supremacist Dylann Roof on hate crime and other charges over the June 17 massacre of nine black church-goers in Charleston, South Carolina.
The 33-count indictment is in addition to South Carolina state murder and attempted murder charges against the 21-year-old suspect, who could face the death penalty if convicted.
"Racially-motivated violence such as this is the original domestic terrorism," said Attorney-General Loretta Lynch in announcing the indictments at a Washington press conference.
"For these crimes, Roof faces federal penalties of up to life imprisonment or the death penalty," Lynch said.
Roof was arrested in North Carolina a day after he allegedly joined an evening bible study class at Emanuel African Methodist Episcopal Church, then shot nine participants with a .45-calibre Glock handgun.
The victims included Emanuel's chief pastor Clementa Pinckney, who was also a South Carolina state senator.
Three people survived the shooting.
A website attributed to Roof was later found to contain racist views towards African-Americans, as well as photographs of Roof brandishing guns and the Confederate battle flag.
Lynch said the US government was charging Roof with nine murders and three attempted murders under a hate crime law that prohibits the use of force to harm an individual on the basis of race or colour.
He is also charged under a second hate crime law that bans the use of force to prohibit the free exercise of religious belief, the Attorney-General said.
"Finally, Roof has been charged with the act of using a firearm in these racially motivated murders and attempted murders," she said.
No decision has been taken on whether to seek the death penalty, Lynch said, adding that consultation with the victims' families would be "an important part of this decision-making process."
South Carolina has no hate crime laws on its books, but the murder charges it is pressing against Roof carry the possibility of the death penalty.
The massacre shocked Americans, occurring as it did in one of the oldest and most famous African-American churches in the South, in a city that was once the American hub of the transatlantic slave trade and, in 1861, the starting point of the Civil War.
It also rekindled vigorous opposition to the Confederate battle flag, with lawmakers voting earlier this month to no longer fly the controversial saltire outside the South Carolina legislature.
"Roof conceived his goal of increasing racial tensions and seeking retribution for perceived wrongs that he believed African-Americans have committed against white people," Lynch said.
"To carry out these twin goals of fanning racial flames and exacting revenge, Roof further decided to seek out and murder African-Americans because of their race," added the Attorney-General, who is African-American herself.
Cornell University law professor Jens Ohlin said any penalty that Roof might get for murder at the state level would dwarf any sentence that may emerge from a federal hate crimes trial.
"But criminal law is about more than just punishment," Ohlin said.
"It is also about signalling an important community value - that criminal conduct motivated by racism or bigotry is especially heinous and hurtful to the fabric of our free society."
South Carolina has carried out 43 executions since January 1985, all for murder, but only one - by lethal injection - since 2009.
The federal government has not carried out an execution since 2003.