Barack Obama
US President Barack Obama speaks during an event marking the 50th Anniversary of the Selma to Montgomery civil rights marches at the Edmund Pettus Bridge in Selma, Alabama,AFP / Getty Images

President Barack Obama has said that despite 50 years of progress, America's racial history "still casts a long shadow".

The US President was speaking at an event in Selma, Alabama, to mark the 50th anniversary of the marches to demand an end to discrimination against black voters.

In a rousing address he said: "We just need to open our eyes, and ears, and hearts, to know that this nation's racial history still casts its long shadow upon us. We know the march is not yet over, the race is not yet won, and that reaching that blessed destination where we are judged by the content of our character - requires admitting as much."

Thousands of people from across the US gathered at the riverside town to commemorate the civil rights march of 1965, when police in Selma beat back crowds attempting to march to the state capital Montgomery to protest over the inability of black people to register to vote.

Barack Obama
S President Barack Obama (6L), First Lady Michelle Obama (4L), former US President George W. Bush (5R), Laura Bush (6R), and US representative John Lewis (5L), Democrat of Georgia and one of the original marchers, lead a walk across the Edmund Pettus Bridge to mark the 50th Anniversary of the Selma to Montgomery civil rights marches in Selma, Alabama.AFP / Getty Images

The violent images of protestors being beaten down and attacked with tear gas and clubs by state troopers were broadcast on national television and the "Bloody Sunday" galvanised America's opposition to racial oppression in the South. Civil rights leader Dr Martin Luther King joined the march which ultimately lead to the passage of the Voting Rights Act.

Leaders in Washington passed the Voting Rights Act five months later.

Paying tribute to those who fought for their basic freedoms and in doing so inspired a generation, Mr Obama described the activists as "warriors of justice" who strove to usher in an era of equality in America.

"So much of our turbulent history - the stain of slavery and anguish of civil war, the yoke of segregation and tyranny of Jim Crow, the death of four little girls in Birmingham, and the dream of a Baptist preacher - met on this bridge," he said.

Barack Obama
US President Barack Obama hugs US Representative John Lewis, Democrat of Georgia, one of the original marchers at Selma.AFP / Getty Images

"It was not a clash of armies, but a clash of wills - a contest to determine the meaning of America."

"From the streets of Tunis to the Maidan in Ukraine, this generation of young people can draw strength from this place, where the powerless could change the world's greatest superpower, and push their leaders to expand the boundaries of freedom," he said.

The President rallied a new generation of Americans to the spirit of the civil rights struggle, warning their march for freedom 'is not yet finished' as he denounced new attempts to restrict voting rights.

Accompanied by FLOTUS Michelle Obama, Mr Obama joined some of the original civil rights marchers to gather at the Edmund Pettus bridge, including Georgia representative John Lewis, a leader of the Selma march who was severely beaten by police in 1965.

"There's still work left to be done," Mr Lewis told the crowd. "Get out there and push and pull until we redeem the soul of America."

Barack Obama
US President Barack Obama (2nd R), First Lady Michelle Obama (C), former US President George W. Bush (2nd L), Laura Bush (L) and US Representative John Lewis, Democrat of Georgia'.AFP / Getty Images

The city of Selma and the historic march to freedom was recently under the global spotlight following the release of the movie Selma and the controversy over the glaring ommission of lack of black filmmakers and stars in the Oscar nominations.

The 50th anniversary comes as the report from the Department of Justice details racial bias in Ferguson, a city which was the scene of violent riots following the killing of an unarmed black man by a white police officer last summer.