Two French tourists, a South Korean national and the U.S. woman were being transported north toward Mali when French special forces stormed their captors' hideout. Two French naval commandos were killed in the mission, which was authorized by President Emmanuel Macron.
While the identity of their captors remains unclear, the hostages were destined to be transferred to a group known as Katibat Macina, French Army Chief of Staff Gen. Francois Lecointre said.
The risk of them ending up with an extremist group in Mali — which would have made efforts to free them impossible — triggered the operation early Friday, Lecointre added.
Led by Malian preacher Amadou Kouffa, Katibat Macina is particularly active in the central Malian region of Mopti close to the border with Burkina Faso, according to Andrew Lebovich, an expert in the region and a visiting fellow at the European Council on Foreign Relations.
Lebovich said it has ties to Ansar ul Islam, a jihadist group that was initially active in northern Burkina Faso but that has rapidly expanded.
Jacob Zenn, a fellow on African affairs at the Washington-based Jamestown Foundation research institute, said Katibat Macina was essentially a Mali-based outgrowth of Al Qaeda in the Islamic Maghreb.
"As they have extended toward the Burkina Faso border, they have basically formed a Burkinabe subgroup of themselves called Ansar ul Islam," he added.
The group aims to gradually set up an Islamic caliphate in the region, according to Zenn.
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In 2017, the group merged with four other Malian Al Qaeda-linked groups under the name Jama'at Nasr al-Islam wal Muslimin or "Group for the Support of Islam and Muslims," according to Human Rights Watch.
While French authorities have said the captors wanted to transfer the hostages to Katibat Macina, they have not given any specific information about who kidnapped the foreign nationals in the first place.
French Armed Forces Minister Florence Parly has said only that there are "two principal terrorist movements that operate in this zone — one is affiliated with Al Qaeda, and the other with the Islamic State."
Analysts said the nature of militant organizations in the region made it difficult to pin down the culprits.
"Groups sometimes share fighters or cooperate, or at a minimum, can occupy territory in proximity to each other without causing problems between the groups," Lebovich said.
"The way you assess who is responsible is by looking at who’s been operating there and what the tactics were like," Zenn added.
Four of the kidnappers were killed and two escaped, according to the French military chief.
Days after the rescue operation, little is known about the American woman who was freed.
As the two French citizens and the South Korean woman were flown back to Paris, the American was nowhere to be seen. It is also unclear where the U.S. woman went missing, but Lecointre said she had been held for 28 days.
The two rescued Frenchmen were kidnapped May 1 while on safari in the Pendjari National Park wildlife reserve in Benin. Their guide was later discovered dead.
Burkina Faso President Roch Kabore said on Twitter on Saturday that he spent time with the three other freed hostages but did not mention the U.S. citizen.
"All our thoughts go to the families of the soldiers and to the soldiers who lost their lives to free us from this hell," ex-hostage Laurent Lassimouillas told reporters as he met with Kabore.
The U.S. Department of Defense has told NBC News that the U.S. woman is in her 60s but did not give any further details.
The State Department confirmed a U.S. citizen was rescued but said "due to privacy considerations, we have no further information to share."
French authorities have said they had no idea the American and South Korean hostages were also being held when the nighttime raid was launched.
"We were not aware of their presence," French Armed Forces Minister Florence Parly told a news conference.
Contacts with the United States and South Korea "show that these countries were probably not aware of the presence of their two nationals on Burkina Faso territory," she added.
Parly called the rescue "an operation of rare difficulty" that grew more complex with the discovery of the American and the South Korean.
Macron attended a ceremony in Paris paying tribute to slain commandos Cédric de Pierrepont and Alain Bertoncello on Tuesday.
Saphora Smith is a London-based reporter for NBC News Digital.
Rima Abdelkader, Associated Press and Reuters contributed.