Obama: 'Voting rights need protecting' 50 years after Selma

President Obama has paid tribute to the demonstrators who were beaten and tear gassed by police 50 years ago in Alabama as they marched for the right of black people to vote.

Speaking in Selma at the Edmund Pettus Bridge where much of the violence took place, President Obama praised the courage of Americans who proved that peaceful protest could lead to change.

But he said that voting rights - what he called America's "crowning achievement" - were now under threat.