The French president has urged citizens not to travel to areas where they risk being kidnapped, as he greeted a man returning after being held hostage for three years by al Qaida's North Africa branch.
Serge Lazarevic arrived in France early today at the Villacoublay airport outside Paris after being released in what some suspect was a prisoner exchange.
His release revived questions about whether governments should negotiate with hostage-takers.
Mr Lazarevic repeatedly thanked Francois Hollande and the government "for having done everything to free me" but neither he nor the president detailed what led to his liberation.
Mr Hollande expressed "extraordinary joy" at his return and urged his compatriots to "avoid zones at risk".
Mr Lazarevic was kidnapped from a hotel in north-east Mali in November 2011.
The liberation came days after the release of two al Qaida fighters imprisoned in Mali for Mr Lazarevic's kidnapping, according to a security official there.
Mr Hollande added: "I want to send a clear, simple message to all our fellow citizens who can be in so-called zones at risk. Make sure not to go where you can get abducted."
The French military is fighting extremists in Africa and the Middle East, and the Islamic State group and al Qaida branches in North Africa and the Arabian Peninsula have identified France and its citizens as potential targets.
Mr Lazarevic and another Frenchman, Philippe Verdon, were kidnapped from their hotel in November 2011. Mr Verdon was found dead last year.
France insists it pays no ransoms and does not exchange prisoners, although Mr Hollande has acknowledged that other countries have done so "to help us".
In the case of Mr Lazarevic, he credited cooperation of the governments of Mali and Niger.