Far-right presidential candidate Marine Le Pen says France should immediately reinstate border checks and expel foreigners who are on intelligence service watch lists, adding that these were steps she would take, if elected.
She also is calling for mosques with ties to extremism to be closed. A translation of one of her latest tweets says: "Hate preachers must be expelled, the Islamist mosques closed."
It comes after Thursday night's killing of a police officer in Paris. The attack was carried out by a French man, but claimed by Islamic State.
"We cannot afford to lose this war. But for the past 10 years, left-wing and right-wing governments have done everything they can for us to lose it. We need a presidency which acts and protects us," Ms Le Pen told reporters at her campaign headquarters.
She has gained some support in the first opinion poll to be held entirely after the Paris attack, but centrist Emmanuel Macron was still seen beating her on Sunday and defeating her in a runoff two weeks later.
Until now, Le Pen had struggled to get the campaign to focus on her party's trademark tough security and immigration stance. By contrast, she has been thrown on the defensive over her position to pull out of the eurozone, a proposal that lacks wide support.
Referring disparagingly to outgoing Socialist President Francois Hollande as "notoriously feeble", Le Pen said: "I only ask one last-ditch effort from him before leaving power: I solemnly ask him to effectively reinstate our borders."
She added: "Elected president of the Republic, I would immediately, and with no hesitation, carry out the battle plan against Islamist terrorism and against judicial laxity."
It is unclear what impact the attack will have on the first round of already very unpredictable presidential elections on Sunday.