MILAN (AP) — The Latest on Italy's referendum on constitutional reforms (all times local):

11:30 a.m.

Premier Matteo Renzi has cast his ballot in a referendum on constitutional reforms that will be decisive for his political future.

Renzi voted at a balloting station in Pontassieve, a Tuscan town about 14 kilometers (nine miles) east of Florence, the city where he was mayor before becoming premier 2 ½ years ago. He was accompanied by his wife, Agnese Landini, who also voted.

After marking the ballot in a booth, Renzi posed for photographers and dropped the form into the ballot box.

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.

Renzi is expected to return to Rome later this afternoon to watch the outcome of the vote.

11 a.m.

Former Italian Prime Minister Silvio Berlusconi has cast his ballot in the referendum on constitutional reforms that is being closely watched abroad to see if Italy is the next country to reject the political status quo.

The former three-time premier has said he would vote "No." He shook hands with election officials and posed for photographers after voting in the capital, Rome.

Berlusconi's Forza Italia party is largely in disarray, with a tax fraud conviction keeping the 80-year-old center-right leader out of public office.

Premier Matteo Renzi says he will resign if the reforms are rejected, and opposition politicians have vowed to press for a new government if voters reject the proposed constitutional changes.

8:05 a.m.

Italians are voting in a referendum on constitutional reforms that is being closely watched abroad to see if Italy is the next country to reject the political status quo.

Premier Matteo Renzi says he will resign if the reforms are rejected in Sunday's vote, and opposition politicians have vowed to press for a new government if voters reject the proposed constitutional changes.

The risk of political instability has triggered market reaction before the vote, with bank stocks sinking and the borrowing costs on sovereign debt rising.

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.

Polls are open Sunday for 16 hours starting at 7 a.m. (0600 GMT).