Florissant - Democratic presidential hopeful Hillary Clinton decried the Charleston church massacre as an act of 'racist terrorism' on Tuesday, and called for the Confederate flag to be removed from the state capital grounds.
Speaking at a church in Florissant, Missouri, Clinton said Americans were struggling to come to grips with Wednesday's killing of nine African Americans at Emanuel African Methodist Episcopal Church by a suspected white supremacist.
"That night, word of the killings struck like a blow to the soul. How do we make sense of such an evil act, an act of racist terrorism perpetrated in a house of God?"
She said the killings by 21-year-old suspect Dylann Roof was an indication of entrenched racism in the United States.
"I know it's tempting to dismiss a tragedy like this as an isolated incident, to believe that in today's America, bigotry is largely behind us. That institutionalized racism no longer exists," she said.
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"But despite our best efforts, and our highest hopes, America's long struggle with race is far from finished."
Clinton's comments came at Christ the King United Church, just 6km from Ferguson, Missouri, where unarmed black teenager Michael Brown was shot dead by a white police officer in August, sparking weeks of protests and a national debate about race relations.
The Emanuel bloodbath has prompted smaller demonstrations, with some, including Governor Nikki Haley calling for the Confederate flag at the state legislature in South Carolina's capital Columbia to be removed.
Clinton said she supported Haley's calls, and said the flag was a "symbol of our nation's racist past that has no place in our nation's present or future".
"It shouldn't fly there, it shouldn't fly anywhere."
She also welcomed the decision by top retailers Walmart, Amazon, eBay and Sears to no longer stock items bearing the controversial banner.
Clinton, a former US secretary of state and ex-senator, has called for tougher gun laws in the wake of the latest tragedy.