ITALIAN premier Matteo Renzi has cast his ballot in a referendum on constitutional reforms that will be decisive for his political future.
Mr Renzi voted at a ballot station in Pontassieve, a Tuscan town about nine miles (14km) east of Florence, the city where he was mayor before becoming premier two years ago.
He was accompanied by his wife, Agnese Landini, who also voted.
Mr Renzi has said he will resign if the referendum fails, although how that plays out politically is likely to depend on the turnout and the margin of the decision.
He is expected to return to Rome later on Sunday afternoon to watch the outcome of the vote.
Earlier former Italian premier Silvio Berlusconi cast his ballot in Rome.
The former three-time premier has said he would vote "No."
Berlusconi's Forza Italia party is largely in disarray, with a tax fraud conviction keeping the 80-year-old centre-right leader out of public office.
Premier Matteo Renzi has vowed to resign if the reforms are rejected, and opposition politicians have vowed to press for a new government if voters reject the proposed constitutional changes.
The referendum aims to streamline Italy's cumbersome lawmaking process by reducing the powers of the Senate while also removing some key decision-making powers from regions.
Italy's interior ministry said turnout was 20.14 per cent of eligible voters by noon on Sunday.
The turnout is on par with the European elections in May 2014, when 20.48 per cent of eligible voters had cast ballots by noon.
