"I would like to cite the question of Libya and the direct threat to our security of the creation -- under our eyes and not far from our borders -- of a new haven for the jihadi terrorist," Valls told a gathering of social democrats, according to a transcript of his speech.
Valls' comments come amid growing concern that the Islamic State group, which has already seized swathes of Iraq and Syria, has also established a foothold in Libya.
The lawless North African country has become fertile ground for jihadists following the ouster of dictator Moamer Kadhafi in 2011.
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Analysts have warned that IS is expected to gain more strength in Libya, and said the international community was running out time to combat its spread there.
"The threat of Islamic State in Libya is set to increase exponentially," analyst Mohamed El-Jareh, from the Atlantic Council's Hariri Centre for the Middle East, said on Friday.
Since Kadhafi was killed, Libya's beleaguered authorities have been struggling to rein in powerful armed militias who are battling for power and the country's oil wealth.
Recent attacks in Libya claimed by IS have boosted concern that some militias have in fact pledged allegiance to the Sunni Muslim extremists.