Mali paid homage on Monday to two French journalists shot dead in the west African nation's rebel-infested northern desert as the hunt for the killers by French troops and Malian security forces intensified.
Malian journalists hold banners during a march on November 4, 2013 in Bamako
Ghislaine Dupont, 57, and Claude Verlon, 55, were kidnapped and killed by what French Foreign Minister Laurent Fabius said were "terrorist groups" in the flashpoint northeastern town of Kidal on Saturday.
"We will do everything to find the culprits," Malian President Ibrahim Boubacar Keita vowed 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.
The victims were flown to Bamako on Sunday night, where hundreds of Malian reporters and RFI colleagues marched through the capital in silent tribute ahead of their expected repatriation late on Monday.
"We organised this silent march to say 'never again' -- the perpetrators of this crime must be punished," said Makan Kone, president of the capital's media association, the Bamako Press House.
Keita later attended a ceremony at Bamako airport with several government ministers in honour of the journalists, at which he said he was in contact with French leader Francois Hollande and the investigation was "progressing".
The president said he thought of Dupont, a correspondent with years of experience reporting on Africa, as his "own daughter".
A police source in Gao, the main city in northern Mali, said "a dozen suspects" had been detained but a source close to Defence Minister Jean-Yves Le Drian denied there had been any arrests.
The killings have 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.
Fabius told RTL radio on Monday that "operations" were under way in Mali in a bid to "identify a certain number of people in camps".
The deaths have highlighted the ongoing security threat just three weeks ahead of parliamentary elections supposed to mark the completion of Mali's transition back to democracy following a military coup in March last year.
There has been an upsurge in violence in the former French colony, where Paris sent troops early this year to drive out Islamists and Tuareg rebels who had seized the country's vast north after the coup.
A UN peacekeeping force is eventually expected to comprise about 12,600 troops and police but Malian soldiers have nevertheless voiced concerns over a planned drawdown of French troops.
Mali is 'most fragile country'
Paris was due to reduce its deployment of 3,000 troops to 1,000 by the end of January but government spokesman Najat Vallaud-Belkacem signalled that the decision might be reversed in light of the journalists' deaths.
"We are probably going to have to further strengthen our presence to be able to counter terrorism," Vallaud-Belkacem said.
Meanwhile the European Union pledged 615 million euros ($830 million) to Bamako as part of a five-billion-euro package of fresh aid for Sahel countries, describing Mali as the "most fragile country" in the region.
A French military patrol found Dupont and Verlon's bodies about 12 kilometres (seven miles) east of Kidal just hours after they were snatched on Saturday, lying by a pick-up truck in which they had been abducted.
They had travelled to Kidal to interview a spokesman for Tuareg separatist group the National Movement for the Liberation of Azawad (MNLA), and were abducted outside his home, according to their employer.
The MNLA described the murders as "heinous" and complained it had been denied the opportunity to help find the killers, despite being the main rebel group in the area.
"They are refusing even to show us the vehicle used for the kidnapping, even though seeing it could put us on the trail of the terrorists," MNLA vice-president Mahamadou Djeri Maiga told AFP.
The MNLA announced late Monday that it was merging with two other rebel groups, the Tuareg High Council for the Unity of Azawad and the Arab Movement of Azawad, to form a united front in peace talks with the authorities in Bamako.
The groups said the decision was "guided by a common political will to prioritise the best interests of the people" of the vast northern desert region they call Azawad, adding that a political solution was the only option for securing peace.
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