Fabius spoke in the Libyan capital, Tripoli, after meeting Monday with Libyan President Mohammed el-Megarif and Prime Minister Ali Zidan.
"There can be no democracy without security. There can be no security without re-establishing the authority of the state," Fabius said in his speech to the parliament.
He urged Libyan authorities to tighten border security. Otherwise, he warned, "Libya could find itself given over to disorder and terrorism."
Since the overthrow of Libyan dictator Moammar Gadhafi in last year's civil war, the country has been struggling to impose control over various militia groups and overcome rivalries among tribes and communities.