The implementation of a controversial voter ID law in at least ten states has angered many in the country's African American and Latino communities. And the leading civil rights group in the US has called it "an attack on democracy from within".

The Republican-backed law requires voters to show government-issued photo identification when they go to the polls in November.

But the US justice department says this would disqualify hundreds of thousands of people from voting.

The issue stoked further controversy recently when a senior Republican official in Pennsylvania said the law would allow presidential candidate Mitt Romney to win the state.