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

Mr Obama was speaking at an event in Selma, Alabama, to mark the 50th anniversary of marches that took place to protest against the lack of voting rights.

"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," he said.

"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."

In March 1965, 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.

The violent images broadcast on national television helped lead to the passage of the Voting Rights Act after protesters were joined by Dr Martin Luther King.

The city has been propelled into the global spotlight again this year with the release of the movie Selma and the controversy over its shortage of Oscar nominations.

The anniversary comes with America digesting the report from the Department of Justice detailing racial bias in Ferguson, a city which saw violent protests over the killing of an unarmed black man by a white police officer last summer.

Mr Obama joined civil rights marchers of 50 years ago at the bridge where police brutality on "Bloody Sunday" galvanised America's opposition to racial oppression in the South.

Thousands from across the US gathered at the riverside town for commemorations.

Mr Obama said the civil rights march of 1965 was a global inspiration for those fighting for freedom.

"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.