Paris Socialist Mayoral Candidate Anne Hidalgo

France's anti-immigrant National Front (FN) made strong gains in the first round of local elections on Sunday as President Francois Hollande's Socialists and his allies suffered losses, according to early exit polls.

The elections to thousands of town halls across France are the first nationwide voter test for Hollande, who came to power in May 2012 and has seen his popularity fall to record lows for failing to rein in unemployment.