"We have decided ... To mobilise 10,000 men to protect sensitive sites in the whole country from tomorrow (Tuesday) evening," Defence Minister Jean-Yves Le Drian said after an emergency security meeting.
"This is the first time that our troops have been mobilised to such an extent on our own soil," he added.
Ahead of the meeting, Prime Minister Manuel Valls said one of the attackers, Amedy Coulibaly, who gunned down a policewoman and four Jewish shoppers at a kosher supermarket, likely received help from others.
"The hunt will go on," he pledged.
The alert level in the shell-shocked country remained at its highest possible, as the interior minister announced the deployment of nearly 5,000 police to guard Jewish schools and places of worship.
Bernard Cazeneuve said he was putting in place a "powerful and durable" system of protection for France's Jewish community, the largest in Europe.
The announcement of the fresh security measures came after more than 1.5 million people in Paris marched Sunday in unity and solidarity for those murdered, in the biggest rally in modern French history.
All major newspapers splashed photos of the sea of humanity on the French capital's streets, with banner headlines reading "A people rise up", "Freedom on the march," and "France stands up".
During an emotional and colourful rally, the crowd brandished banners saying "I'm French and I'm not scared".
In tribute to the cartoonists slaughtered at the offices of satirical magazine Charlie Hebdo, the crowd also held aloft signs saying: "Make fun, not war" and "Ink should flow, not blood".
