France's far-right National Front has won a run-off vote in a local election that drew widespread attention amid signs that the once-shunned party is gaining strength.

The by-election saw National Front candidate Laurent Lopez defeat center-right UMP candidate Catherine Delzers to win one of 43 seats on the Var department council.

France is made up of more than 100 departments; five or so departments make up a region.

A call by the ruling Socialist party of President Francois Hollande to vote for the UMP candidate fell flat, with the Lopez taking 53.9 percent of the vote.

More than half of the eligible voters stayed home.

Surveys suggesting the National Front's strength is growing ahead of municipal and European parliamentary elections have alarmed France's mainstream parties.