North Carolina Governor Pat McCrory has signed into law a fiercely contested initiative making sweeping changes in how and when the state's voters can cast their ballots.

Hours after Monday's signing, the American Civil Liberties Union announced it and two other groups had filed a lawsuit challenging the legislation. The Republican-backed measure was opposed since it was proposed.

There was no bill-signing ceremony. McCrory's office issued a statement saying he signed the legislation and posted a 95-second message on YouTube giving his reasons.

Republicans have said the legislation is meant to prevent voter fraud, which they claim is both rampant and undetected. But non-partisan voting rights groups, Democrats and libertarians suggested the true goal was to suppress voter turnout, especially among blacks, the young, the elderly and the poor.