Saturday's mobilisation announcement came after President Macron held an emergency security cabinet meeting on Friday evening.
France is mobilising 7,000 soldiers and increasing its alert status to "emergency attack" level after the death of a teacher in the northeast town of Arras, stabbed to death Friday by a former student with a record of Islamic radicalisation.
President Emmanuel Macron made the decision after convening an emergency meeting of his security cabinet on Friday night.
Macron has described the stabbing attack, which left two other staff members at the school seriously injured, as "Islamist terrorism."
He ordered "up to 7,000 soldiers from the Sentinelle force, who will be deployed between now and Monday evening and until further notice", the Elysée Palace said on Saturday morning.
What happened in Arras?
French authorities have opened anti-terror investigations after the Arras attack.
Local police say a man armed with a knife killed a teacher and left two other people wounded in a high school in the town of almost 41,000 people on Friday morning. The attacker was arrested at the scene.
The incident took place at the Gambetta high school, which is located in the town centre, and police say the attacker shouted "Allah Akbar" - "God is great" in Arabic.
He has been named as 18-year-old Mohammed Mogouchkov, a former student at the school of Chechen origin who was the subject of "active monitoring" by France's General Directorate of Internal Security DGSI.
Mogouchkgov had been stopped and searched as recently as last week but was released as there was no reason to hold him, officials said.
No high school students were injured in the attack, but a security guard and a teacher were gravely wounded after suffering several stab wounds.
Macron visits scene, then holds security cabinet meeting
France's President Emmanuel Macron visited the school on Friday afternoon, and called on people to remain "united" and to "stand together" in the face of "the barbarity of Islamist terrorism."
Speaking in the courtyard of a building near the school where Friday morning's deadly attack took place, Macron said "the choice is made not to give in to terror, not to let anything divide us."
Later on Friday evening, Macron held an emergency meeting of his security cabinet in Paris.
Senior government ministers, police, military and intelligence officials attended the meeting which came after a second security incident was confirmed.
A 24-year-old man known to have been "radicalised" was arrested and placed in police custody for carrying a knife as he left a mosque in Limay on the outskirts of Paris.
The Versailles public prosecutor's office confirmed the man's arrest.