RFI described Dupont, 51, and Verlon, 58, as professionals with long experience in challenging areas.
Dupont was a journalist who was "passionate about her job and the African continent that she covered since joining RFI in 1986," it said in a statement. Verlon was "used to difficult terrain throughout the world."
Staff members "are all in shock, profoundly saddened, indignant and angry," it said.
France opened a judicial investigation into the kidnappings and deaths "linked to a terrorist enterprise," the prosecutor's office said.
Suspicion in Saturday's killings immediately fell on Islamist militants.
"From the information I have, their throats were cut. We don't know for sure who took them, but the reports we are hearing indicate that they were Islamists," said Lassana Camara, the deputy prefect of Tinessako.
Several Kidal officials interviewed by telephone said that the RFI journalists were abducted after an interview at the house of Ambeiry Ag Rhissa, the acting head of the National Movement for the Liberation of the Azawad, or NMLA, a Tuareg separatist movement whose rebels invaded northern Mali last year. Those rebels were later chased out by al-Qaida's fighters in the region but have returned to prominence in Kidal in recent months.
Rhissa said in telephone interview with the France 24 TV station that he heard sounds and walked outside, where a vehicle had pulled up beside the journalists' car. A man pointed a gun at him and said "Go inside, go inside."
When they took off, "I heard a single gunshot," he said. Rhissa said he didn't see how many men were in the vehicle but said he was told by several people there were four.
Lt. Col. Oumar Sy, a Malian officer stationed in Kidal and involved in the investigation, said that everything pointed to the NMLA.
"We are in a town that is in the de facto hands of the NMLA. We learn that these poor people are taken in front of the house of an NMLA leader. No one lifts a finger to help them. What conclusion would you come to?" he said.
The French-led military operation succeeded in restoring government rule in all the regions formerly held by al-Qaida, with the exception of Kidal. Although the Malian military returned this summer, they remain mostly confined to their military base, largely unable to patrol the streets, where the NMLA rebels can still be seen zooming through the sand-enveloped paths aboard pickup trucks bearing the NMLA flag.
The French president called key ministers for a Sunday meeting in a first step to find out how and why the journalists were killed.
Hollande and Malian President Ibrahim Boubacar Keita agreed in a phone call "to follow without let-up the fight against terrorist groups that remain present in northern Mali," according to a statement from Hollande's office.
The executive director of Reporters Without Borders, Christophe Deloire, expressed disgust in an interview with The Associated Press that "two experienced journalists can lose their lives because nefarious militias consider it normal to shoot."
Since 2003, northern Mali also has acted as a rear base for al-Qaida's North African branch, which has used the country's vast deserts north of Kidal to train fighters, amass arms and prepare for war. They have bankrolled their operations by kidnapping Westerners, especially French nationals.
According to global intelligence unit Stratfor, al-Qaida in the Islamic Maghreb has carried out at least 18 successful kidnappings of foreigners in the past decade, netting at least $89 million in ransom payments.
Just last week, four Frenchmen kidnapped three years ago in neighboring Niger were released by the terrorist group in the deserts of northern Mali, allegedly for ransom of more than 10 million euros ($13.5 million), according to Pascal Lupart, the head of an association representing the friends and families of hostages held by the group.
Al-Qaida in the Islamic Maghreb embedded itself in northern Mali in part by forging alliances with the Tuareg people, who have agitated for independence for the past half-century. Several of al-Qaida's local commanders are believed to be Malian-born Tuaregs, with ties to both Kidal and the local separatist movement, the NMLA.
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Ganley reported from Paris. Bastien Inzaurralde contributed from Paris.
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