Jihadists in Mali have freed a prominent opposition leader kidnapped earlier this year and a French aid worker held captive for almost four years, in a major exchange of prisoners with the country’s new transition government.

Soumaïla Cissé, a 70-year-old former presidential candidate, was kidnapped in March while campaigning in his home town in the restive north of the country.

Sophie Pétronin, thought to be the only French citizen held hostage in the world, ran a Swiss charity for malnourished children and orphans before she was abducted on Christmas Eve in December 2016, in the northern city of Gao.

The jihadist group Jama’at Nusrat al-Islam wal-Muslimin (JNIM), an affiliate of al-Qaida, claimed responsibility for the kidnappings – the most high-profile in a wave of abductions – as numerous militant groups have waged a bloody insurgency that has devastated the region and fuelled political upheaval in Mali.

Following their release, Cissé and Pétronin were on a flight to the capital, Bamako, on Tuesday, local media and the Associated Press reported.

Hopes of a deal had been building in recent days, amid reports that nearly 200 detained jihadists would be freed by security forces. Multiple planes carrying jihadist prisoners reportedly flew to the northeastern town of Tessalit on Sunday.

Pétronin’s son, Sébastien Chadaud-Pétronin, arrived in Bamako from Paris on Tuesday but remained cautious. “We’ve already lived through moments like this for four years,” he told AFP.

Pétronin’s nephew, Lionel Granouillac, told the French TV station BFM: “She is free, even if the French authorities have not confirmed it. Sébastien, my cousin, is on site in Bamako. They are preparing to welcome her.”

Pétronin’s family have led a desperate campaign for her release. She had been suffering from cancer and malaria when she was abducted while heading the charity Association Aid to Gao. In a video released by the jihadists in June 2018 she appealed for help from the French president, Emmanuel Macron.

The new transition government in Mali, in power following a military coup in August, has sought to turn the country round after a tumultuous period of instability. Opposition figures in the new government had sought assurances that Cissé, a prominent political veteran, would be freed.

Earlier today, the 15-country west African regional bloc Ecowas announced a lifting of sanctions imposed against Mali after the coup. “Heads of state and government have decided to lift sanctions” to “support” the new civilian rule, the statement said.

The Malian president Ibrahim Boubacar Keïta was deposed in August a year into his second term, following months of mass protests against his government.

Discontent at surging jihadist violence in the region, despite the contentious presence of thousands of French soldiers, teams of US special forces, regional armies and UN peacekeepers, fuelled anger at Mali’s government. A flailing economy and accusations of government corruption following disputed election results in April sparked mass demonstrations that brought the country to a tipping point.

Mali’s military junta, known as the National Committee for the Salvation of the People, initially proposed a three-year period of transition yet, ceding to international and domestic political pressure, agreed to an 18-month transition period before new elections.

Ecowas had demanded that the government be a civilian-led administration as a condition to relieve sanctions, which stopped financial transfers into the country and shut regional borders with Mali.

A 25-member cabinet announced yesterday met those conditions, while members of the junta retain four key posts, with their leader, Colonel Assimi Goïta, appointed as vice-president.