Nearly 60 per cent of Italy's voting population have cast their ballots in a referendum on constitutional reform that will decide the political future of Prime Minister Matteo Renzi, who has vowed to resign if he loses.
Financial markets and Europe's politicians fear victory for the opposition 'No' camp could cause political instability and renewed turmoil for Italy's battered banks, pushing the euro zone towards a fresh crisis.
About 51 million Italians are eligible to vote on Renzi's plan to drastically reduce the role of the upper house Senate and claw back powers from regional authorities.
By 7pm local time more than 57 per cent of Italians had gone to their polling stations, the Interior Ministry said, above the 42 per cent registered at the same time in the May 2014 European parliament election, when Renzi's Democratic party drummed up high support.
Regions in the South, home to over a third of the electorate, once again registered the lowest turnout figures while voters in the central region of Emilia Romagna, traditionally close to the left-wing, were the most active, according to figures released earlier in the day.