The son of a French aid worker kidnapped in Mali said Wednesday he was still awaiting news about his mother, as governments maintained their silence despite speculation about her possible release.

Hopes that 75-year-old Sophie Petronin and abducted Malian opposition leader Soumaila Cisse may soon be released surged at the weekend when security officials said Mali's new government had freed scores of jihadists.

But Petronin's son, Sebastien Chadaud, who flew to Mali's capital Bamako on Tuesday, said he had no information about his mother.

"We still don't know whether she's part of these negotiations," said Chadaud, who explained he had come to Bamako to be by his mother's side should she be freed.

The Malian and French governments have neither confirmed nor denied a possible prisoner swap, despite some new reports and feverish speculation online.

Petronin was abducted by gunmen on December 24, 2016, in the northern city of Gao, where she worked for a children's charity. She is the last French national held hostage in the world.

Cisse, a 70-year-old former opposition leader and three-time presidential candidate, was kidnapped on March 25 while campaigning in his home region of Niafounke, in central Mali, ahead of parliamentary elections.

Islamist fighters linked to al-Qaeda are thought to hold both Petronin and Cisse.

Sophie Petronin, 75, was abducted nearly four years ago
Sophie Petronin, 75, was abducted nearly four years ago SITE INTELLIGENCE GROUP / -

Several French security officials expressed their frustration to AFP about the noise surrounding the possible prisoner swap.

France's government has also declined to comment despite significant interest in Petronin's release.

"I don't want to interfere in this situation," French government spokesman Gabriel Attal said on Wednesday.

He added that the issue was "extremely sensitive" and needed to be approached with the "utmost discretion".

An al-Qaeda-affiliated media outfit has nonetheless said that Bamako has released 206 fighters as part of a swap, the jihadist-surveillance group SITE Intelligence said this week.

But a high-ranking French official, who requested anonymity, said he was "very doubtful" about the number of jihadists possibly released, suggesting that French authorities were not closely involved in such a plan.

Mali's former colonial ruler France has 5,100 soldiers deployed across the Sahel region as part of its anti-jihadist Operation Barkhane.

Swathes of the vast West African nation of 19 million lie outside government control, with Mali struggling to contain an Islamist insurgency that first erupted in 2012.

Thousands of civilians and soldiers have been killed and hundreds of thousands of people have fled their homes.

Several foreigners have also been kidnapped in Mali, where armed groups are still holding at least eight Western hostages.

Anger at the abduction of Cisse in March was a factor in a groundswell of protests against President Ibrahim Boubacar Keita, who was finally toppled by young army officers on August 18.