"A dozen suspects have been arrested since the murder of two Radio France Internationale (RFI) journalists," said a police source in Gao, the main city in northern Mali.
Radio France Internationale (RFI) journalist Ghislaine Dupont, 57, and sound technician Claude Verlon, 55, were kidnapped and killed by what Foreign Minister Laurent Fabius coined "terrorist groups" in the flashpoint northeastern town of Kidal on Saturday.
Their murder has shaken France, which just days ago was celebrating the return of four hostages who had been held for three years after being abducted in Mali's neighbour Niger.
On Monday, Fabius told RTL radio "operations" were under way in Mali in a bid to "identify a certain number of people in camps."
But a source close to Defence Minister Jean-Yves Le Drian who refused to be named told AFP French forces had "information" that could allow the murderers to be tracked down.
Dupont and Verlon's bodies were found riddled with bullets just hours after they were kidnapped on Saturday, lying by a pick-up truck they had been abducted in.
Fabius said Dupont was killed with two bullets in the chest while Verlon "received three bullets in the head."
"When the French forces arrived behind the pick-up, they saw someone escaping not far away, around 1,500 metres (5,000 feet) away, they followed him but did not catch him."
The arrests came as Malian president Ibrahim Boubacar Keita vowed that everything would be done to find the killers of the journalists.
"We will do everything to find the culprits," Keita said as he met in Bamako with members of the management of Radio France Internationale (RFI), the station where the pair worked.
"Today even, we have opened a criminal investigation into the killings and tonight French investigators are expected here to work hand-in-hand with their Malian counterparts," he added.
"We share the shock, we too are overwhelmed by the emotion," he said, announcing that he would attend a ceremony Monday in honour of the journalists and that he would decorate them posthumously on behalf of Mali.
The two veteran journalists had travelled to Kidal to interview a spokesman for the Tuareg separatist group the National Movement for the Liberation of Azawad (MNLA), and were abducted outside his home, according to their employer.