Marine Le Pen appeared at a political rally at a farm near Limoges.
The Front National leader delivered a speech vowing to protect farmers who have been “abandoned” and “forgotten” by city-centric politics.
More than 500 people turned out to hear the presidential hopeful at Puybonnieux farm in Pageas.
Marine Le Pen delivered a defiant speech hours after arsonists targeted her office
The Front National leader delivered a speech vowing to protect farmers who have been “abandoned” and “forgotten” by city-centric politics
Her speech came hours after arsonists hit Ms Le Pen’s Paris headquarters.
Police said the attack caused minor damage with the Front National leader blaming leftist groups for the arson attempt.
The police source said the ground floor of the central Paris building was targeted and graffiti mentioning Ms Le Pen's National Front was found nearby.
Interior Minister Matthias Fekl condemned the attack.
He said: “These are unacceptable acts, the democratic debate must take place in the ballot box," Fekl told RTL radio, without giving any details about the attack itself.
“We have been in touch with the National Front candidate's team since last night and will see with them if it is necessary to strengthen security procedures.”
Some polls suggest Ms Le Pen will win the first round
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Marine Le Pen met rural supporters at a rally near Limoges
Ms Le Pen told France 2 television she believed a leftist group was responsible.
She said: “I assume this is due to a small leftist group. These groups act in total impunity.”
AFP news agency said a group calling itself "Combat xenophobia" contacted them to claim responsibility for the arson attempt.
Polls put Emmanuel Macron as Ms Le Pen's main challenger
Recent polls show the French election race becoming tighter with an Ifop-Fiducial poll saying Ms Le Pen will win the first round on April 23 with 23.5 per cent compared to her main challenger Emmanuel Macron on 22.5 per cent.
According to the poll Mr Macron is expected to beat Ms Le Pen in the second round on May 7 by 58.5 per cent to 41.5 per cent.
Things you didn't know about Marine Le Pen
Wed, April 5, 2017
Marine Le Pen is a French politician who is the president of the National Front, a national-conservative political party in France and one of its main political forces.
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Described as more democratic and republican than her nationalist father, she has led a movement of "de-demonization of the Front National" to detoxify it and soften its image
But a Harris Interactive poll for LCP says Mr Macron will win the first round with 24 per cent over Ms Le Pen's 22 pr cent.
The poll says Mr Macron is seen as defeating Ms Le Pen in the second round with 67 per cent, up four points since April 7, against her 33 per cent.