Italy's center-left will have to choose between a veteran party official and the 37-year-old mayor of Florence after a primary aimed at choosing a candidate for premier failed to produce an outright winner.

Virtually complete results give the 61-year-old leader of the Democratic Party Pier Luigi Bersani 44.9 percent of the votes while Matteo Renzi got 35.5 percent among the five candidates who ran in Sunday's primary.

The party has been leading in opinion polls.

Sunday's vote was nearly overshadowed by speculation about the political ambitions of Italy's current premier, Mario Monti, and whether former Premier Sylvia Berlusconi will run for office for a fourth term.