France is mobilizing 10,000 troops to boost security after last week’s deadly attacks, and will send thousands of police to protect Jewish schools.
Defence Minister Jean-Yves Le Drian said troops would be in place from Tuesday in the most sensitive areas.
The comments came as the French cabinet held a crisis meeting on security.
Seventeen people were killed in Paris last week in attacks at satirical magazine Charlie Hebdo, on a police officer, and at a kosher supermarket.
On Sunday, an estimated 3.7 million people turned out to show solidarity with the victims, including 1.5 million people in Paris.
About 40 world leaders joined the start of the Paris march, linking arms in an act of solidarity.
In Paris on Monday, President Francois Hollande held a crisis meeting with top officials.
Mr Le Drian said the deployment of troops represented the largest ever mobilisation of troops within France, and was needed because “threats remain present”.
Interior Minister Bernard Cazaneuve announced that nearly 5,000 members of the security forces would be sent to protect France’s 717 Jewish schools, and that troops would be sent as reinforcements over the next two days.
Last week, Mr Valls admitted there had been “clear failings” after it emerged that the three gunman involved in the attacks – Said and Cherif Kouachi and Amedy Coulibaly – had a history of extremism.
The Kouachi brothers were on UK and US terror watch lists and Coulibaly had previously been convicted for plotting to free a known militant from prison. Coulibaly met Cherif Kouachi while in jail.
Coulibaly and the two brothers were shot dead on Friday after police ended two separate sieges.
Coulibaly killed four people at a kosher supermarket in eastern Paris on Friday before police stormed the building. He is also believed to have shot dead a policewoman the day before.
Ahead of Sunday’s rally in Paris, a video emerged appearing to show Coulibaly pledging allegiance to the Islamic State militant group.
In the video, he said he was working with the Kouachi brothers: “We have split our team into two… to increase the impact of our actions.”
The Kouachi brothers claimed they were acting on behalf of Yemeni branch of al-Qaeda (AQAP). But experts say it is highly unlikely that Islamic State and al-Qaeda, rivals in the Middle East, would plan an attack together.
The attacks in Paris started last Wednesday, when the Kouachi brothers raided the offices of the satirical magazine Charlie Hebdo, killing 12 people – including eight journalists and two police officers.
French police are still hunting for accomplices of the three gunmen, including Hayat Boumeddiene, Coulibaly’s partner.
However, she is believed to have left France before the attacks. The Turkish foreign minister said she had arrived in Turkey on 2 January from Madrid, before continuing to Syria six days later.
France will remain on high alert in the coming weeks.
In London, Prime Minister Cameron consulted senior intelligence and security officials on Monday over Britain’s response to the attacks in France.