Pioneering US civil rights activist Julian Bond, who once chaired the board of the National Association for the Advancement of Colored People (NAACP), has died aged 75.
Bond died late on Saturday (local time) in Fort Walton Beach, Florida, the Southern Poverty Law Center said in a statement on Sunday.
"The country has lost one of its most passionate and eloquent voices for the cause of justice," said the center, where Bond served as president from 1971 to 1979.
"He advocated not just for African Americans, but for every group, indeed every person subject to oppression and discrimination."
Originally from Tennessee, Bond was at the forefront of America's civil rights movement, which demanded equal rights for African Americans.
US President Barack Obama said he was "privileged" to call Bond a friend, and hailed him as a hero.
"Julian Bond helped change this country for the better. And what better way to be remembered than that," said Obama.
Bond was a founding member of the Student Nonviolent Coordinating Committee, and helped to organise protests at segregated facilities in the 1960s.
"Sit-ins" were being staged across the US South, inspired by four men who dared to sit at a whites-only lunch counter in Greensboro, North Carolina in 1960.
That movement ultimately triggered his involvement in the student movement in Georgia.
Looking back on the civil rights campaign of the 1960s and beyond, Bond said the movement was formed somewhat "unthinkingly".
"We didn't plot it, we didn't plan it. We didn't say, 'Now let's work on this issue. Now let's work on that issue.' The issues seemed to come to us," he said.
Bond's career in student activism eventually led him to politics. He was elected to the Georgia House of Representatives in 1965 and went on to serve for two decades in the Georgia legislature.
He was a vocal opponent of the Vietnam War, and white members of the Georgia House of Representatives refused to seat him because of his opposition to the conflict, according to the NAACP.
The Supreme Court, in 1966, ruled that the House had denied Bond his freedom of speech and had to seat him.
In 1998, he became NAACP chairman and served for 11 years. He remained president emeritus of the Southern Poverty Law Center until his death.
"#JulianBond, a friend & fellow traveler who with courage, set the moral & academic tone of our generation. RIP," said civil rights activist Jesse Jackson on Twitter.
Former president Bill Clinton and his wife Hillary said Bond "helped us to become a more perfect union and always pushed us to do better".
Bond is survived by his wife, Pamela Horowitz, a former attorney at the Southern Poverty Law Center, and his five children.