WASHINGTON, United States (AFP)— US President Joe Biden offered a potent condemnation of racist extremism Sunday after a murderous rampage in Buffalo, and he called for citizens to end the hate that remains a “stain on the soul of America.”

“A lone gunman, armed with weapons of war and a hateful soul, shot and killed 10 innocent people in cold blood at a grocery store on Saturday afternoon” in western New York state, Biden said in Washington at a service for fallen US police officers.

“We must all work together to address the hate that remains a stain on the soul of America,” the president said.

US authorities were “still gathering the facts,” Biden added.

But he noted that the Justice Department has announced it is investigating the rampage “as a hate crime, racially motivated act of white supremacy and violent extremism.”

“Hearts are heavy once again,” Biden said, “but our resolve must never, ever waver.”

The suspected shooter was arrested at the scene in Buffalo, where 13 people in total were shot, 11 of them black.

Police rushed to respond to emergency calls and eventually subdued and detained the 18-year-old suspect, who they said was wearing body armour, carried a semi-automatic assault rifle, and live-streamed the horrific attack on a social media platform.