French Interior Minister Manuel Valls on Tuesday pledged to strengthen security measures and to be vigilant to secure French citizens from potential terrorists' menaces trigged by Paris' intervention in Mali.

"Caution should be exercised. But what I can assure to the French is that the utmost vigilance will be used to prevent acts on our soil," the minister told news channel BFMTV.

"Our intelligence services both inside and outside the country, are particularly vigilant... and we also monitor individuals who want to go to Syria, Afghanistan, and of course the Sahel," he said.

French President Francois Hollande on Saturday evoked Vigipirate, France's national security alert system, following the country's military commitment to help Malian authorities stop the offensive by the rebels

The Vigipirate plan has four alert levels: yellow, orange, red and scarlet, from the lowest to the highest.

The alert level of "reinforced red" is usually in force during sensitive periods such as Christmas and New Year. The alert "scarlet" was briefly imposed in March 2012 in France's Midi-Pyrenees region at the time of the killing spree by Mohamed Merah in Toulouse and Montauban.