The move comes after Thursday night's shooting in central Paris, Prime Minister Bernard Cazeneuve said on Friday.
One policeman was killed and two officers seriously injured by an extremist in a shooting on the Champs Elysees.
Paris Prosecutor François Molins said the gunman has been identified and authorities are still trying to determine whether he had any accomplices.
France deployed security forces to ensure citizens' protection during the presidential election
Authorities are committed to protect the fundamental democratic process of France
The suspect was reportedly already known to police after he was identified from papers left in his car.
Speaking after an emergency meeting of top security officials, Mr Cazeneuve said all elite units were on top alert for the election to back up the 50,000 police already earmarked for special election duty.
Champs Elysees' suspect was reportedly already known to police
Shocking images from the Champs Elysees terror attack
Fri, April 21, 2017
One policeman has been killed and two officers seriously injured by an extremist in a shooting on the Champs Elysees in Paris
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A damaged window is pictured on the Champs Elysees Avenue the day after a policeman was killed and two others were wounded in a shooting incident in Paris
He said: "The goverrnment is fully mobilised. Nothing must be allowed to impede the fundamental democratic process of our country.
"It falls to us not to give in to fear and intimidation and manipulation which would play into the hands of the enemy."
The first round in France's two-stage election will be held on Sunday with a second final round on May 7.