French conservatives are voting in a nationwide primary to choose their nominee for next year's presidential election, after a campaign marked by concerns about immigration and Islamic extremism.

Seven candidates are competing Sunday in the first round of the primary. A runoff will be held between the top two vote-getters a week later.

The three leading candidates are former president Nicolas Sarkozy and former prime ministers Francois Fillon and Alain Juppe.

The candidates have been keeping a close eye on far-right candidate Marine Le Pen, whose criticism of immigration and Muslim practices resonates with many voters.

It's the first such primary organized by France's conservatives, making the outcome hard to predict. Candidates previously were designated internally.

Results from the first-round voting are expected late Sunday.