The US Justice Department have said that it will sue the state of North Carolina for racial discrimination in its tough new voting rules.

President Barack Obama's administration has sought to fight back against a Supreme Court decision that freed southern states from federal oversight of their elections contained in the 1965 Voting Rights Act.

North Carolina has instituted a new law scaling back the period for early voting and imposing stringent voter identification requirements.

At least five southern states are adopting stricter voter ID and other election laws that Republicans insist are vital to stop voter fraud - despite the low levels of such crimes.

Civil rights groups argue that the tough new laws are intended to make voting more difficult for minorities and students - groups that lean toward Democrats - in states with histories of disenfranchising black voters.

In the North Carolina lawsuit, the government will challenge requirements that eliminate the first seven days of early voting opportunities and eliminate same-day voter registration during the early voting period.

Same-day registration allows voters to cast a ballot immediately after presenting election officials with proof of identity.

It will also challenge a provision that requires voters to present government-issued identification before casting their ballots.

A recent North Carolina board of elections survey found that hundreds of thousands of registered voters did not have a state-issued ID.

Many of those voters were young, black, poor or elderly.