A supporter of football team Nice wears a tee shirt reading “Fck Isis” as he cheers before the French L1 football match between OGC Nice and Rennes on August 14, 2016, at the Allianz Riviera stadium in Nice, southern France. AFP

PARIS, France — A former French soldier, arrested last week near an airbase, proclaimed allegiance to Islamic State of Iraq and Syria (ISIS) group jihadists and admitted he was planning an attack, in a letter seen by AFP on Wednesday.

The suspect, who was seized two days before France’s presidential election run-off vote, is said to be psychologically unstable.

He was arrested close to an airbase at Evreux, northwest of Paris by police who found guns hidden nearby and several ISIS flags in his car.

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“My name is Alain Feuillerat, a Muslim soldier defending my fatherland,” he said in the message seen by AFP.

“I was preparing, with Allah’s help, an attack against the Evreux-Fauville airbase,” in the one-and-a-half page letter which mixed criticism of France with religious statements.

The same text was found on a computer memory stick in his car, according to a source close to the enquiry.

“This attack was not designed to kill the maximum number of people but above all to show our determination,” he continued in the message which was dated April 27 but posted in the mail on May 5, the day of his arrest.

The computerized message had two photos attached. One showed the suspect dressed as an Islamic State group fighter, the other was a photo of his French passport.

Feuillarat, 34, remains in detention and was on Monday charged with a terrorist act and with attempting to break into a military area.

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Since being detained he has admitted planning an attack in France because, he said, he was unable to join up with ISIS fighters in Syria.

The former soldier quit the army in 2013 after ten years of service.

He converted to Islam and had been under close surveillance since 2014 due to his radicalization.

France has been hit by a string of Islamist attacks, most claimed by ISIS, since 2015, with over 230 people killed in all.

The presidential election went off without a hitch on Sunday but the prior campaigning was overshadowed by security worries.

Karim Cheurfi, a 39-year-old Frenchman, shot and killed a police officer and wounded two others on the Champs Elysees avenue days before the first round of voting in April, in an attack claimed by the Islamic State group. Cheurfi was killed by police gunfire. CBB/rga