Radio journalists Claude Verlon and Ghislaine Dupont were abducted after interviewing a member of the MNLA Tuareg separatist group in northern Mali.
Their bodies were found on Saturday by a French patrol 12km (eight miles) outside Kidal, the birthplace of a Tuareg uprising last year that plunged Mali into chaos.
Full details of why the journalists were killed and who carried out the attack were not clear. "The assassins are those that we are fighting, the terrorist groups that refuse democracy and elections," Foreign Minister Laurent Fabius said.
He said one of the victims had been shot twice, the other three times. French forces searched for the attackers.
Paris launched air strikes and sent soldiers into Mali at the start of the year to drive back al Qaeda-linked rebels it said could turn the West African country into a base for international attacks.
Although Malian, UN and French troops are stationed in Kidal, none are heavily deployed. There are some 200 UN peacekeepers who are in control of security and France has about 200 troops.
Malian President Ibrahim Boubacar Keita and President Francois Hollande spoke by phone on Saturday. "The two heads of state agreed that the situation in Kidal was unacceptable and that a change was necessary to ensure the security of all Malians and foreigners present there," a government spokesman said.
The deaths came days after four French hostages kidnapped in Niger by al Qaeda were released. They had been held for three years.