Media playback is unsupported on your device Media caption Holder: North Carolina's new voting law is "inconsistent with our ideals as a nation"

The US justice department has said it will sue the state of North Carolina in an attempt to block a series of new restrictions on voting.

Civil rights groups say the law requiring photo ID to cast a ballot discriminates against minorities and poor people, who tend to vote Democrat.

North Carolina's Republican governor says it protects against voter fraud.

A June Supreme Court ruling enabled states to pass new restrictions, over the objections of the White House.

On Monday, US Attorney General Eric Holder - an appointee of Democratic President Barack Obama - said his agency would file the suit in federal court in North Carolina to challenge its "highly restrictive" and "troubling" new voting restrictions.

"[The] clear and intended effects of these changes would contract the electorate... on account of race," he said of North Carolina's legislation.

"We will show that they were discriminatory both in intent and in impact."

Under the North Carolina law, which was signed by the state's Republican governor Pat McCrory last month, voters will be required to show photo identification at the polls, among other provisions.

At the time, Mr McCrory said the new law would protect the integrity of the election process.

'Aggressive action'

The law follows on a June US Supreme Court ruling that invalidated portions of the 1965 Voting Rights Act.

That act had required jurisdictions with a history of racial discrimination to receive federal approval before making changes to their voting laws.

Soon after that decision six states passed voter ID laws.

Analysts say there is no evidence of widespread voter fraud, and some Democrats and civil rights groups say the laws are intended to suppress the Democratic vote.

The Obama administration has vowed to continue challenging the new voting restrictions in court, arguing they effectively disenfranchise minorities, poor people and students, who disproportionately lack identification cards required by the laws.

"Neither the president, nor I, nor the department I am honoured to lead, will waver in our determination to stand vigilant against changes that may hamper voting rights," Mr Holder said earlier this month.

"We will not hesitate to take appropriately aggressive action against any jurisdiction that attempts to hinder access to the franchise."

As part of its lawsuit against North Carolina, the justice department will reportedly challenge four provisions of the state's new voting law.

Those include the stricter voter identification requirement, the elimination of seven days of early voting before official election day, the elimination of same-day voter registration during an early-voting period, and a limit on the counting of some provisional ballots.