Details of the attack remain murky, and members of the patrol have given conflicting accounts of it. It is unclear whether the patrol was simply ambushed, or whether it was attacked after the troops were reassigned to support a separate, clandestine counterterrorism mission against Islamist militants in the area.
Aid workers and tourists have long been urged to avoid the area where the attack occurred, near Niger’s border with Mali, because of the presence of both Al Qaeda- and Islamic State-affiliated groups.
The extent of Mr. Sahraoui’s ties with the Islamic State is unclear. The website in Mauritania that carried the group’s statement on Friday is an outlet favored by Mr. Sahraoui’s former colleagues in Al Qaeda, not by the Islamic State. The area in which Mr. Sahraoui’s group operates contains some of the most forbidding terrain on the planet, a landscape of undulating dunes where cellphone towers are few and far between.
“There is a lot we don’t know about how his operation connects back to the mother ship — what’s the connective tissue?” said Thomas Joscelyn, an analyst who has tracked the group for years as a senior fellow at the Foundation for Defense of Democracies in Washington. “There are a lot of possibilities and many factors in play.”
The remoteness of the area in which Mr. Sahraoui’s group operates, and the difficulty of getting reliable cellphone signals or internet access, could be one factor to explain the delay in releasing the statement. Another possibility is that the Islamic State’s media apparatus was disrupted after the group lost nearly 98 percent of its territory in Iraq and Syria.
Additionally, there have been reports of unrest among from Al Qaeda loyalists after Mr. Sahraoui made his pledge of allegiance to the Islamic State. “There were even reports at one point that he was injured in a shootout with Al Qaeda,” Mr. Joscelyn said.
Mr. Sahraoui cut his teeth in Al Qaeda’s branch in the region, which reported to Osama bin Laden through letters that were carried across the desert by couriers. He joined the Qaeda branch sometime in 2010, according to one account, and became a deputy to Abdelhamid Abu Zeid, one of Al Qaeda’s most notorious commanders in the area and among the first to discover that foreigners were lucrative bargaining chips. He bankrolled his operations through kidnappings for ransom, pioneering a business model that was later adopted by the terrorist group in Yemen, Syria, Afghanistan and elsewhere.
By 2011, Mr. Sahraoui was in charge of taking care of foreign hostages kidnapped by the group, according to Mariasandra Mariani, an Italian who was held by him for more than a year after her abduction in Algeria on Feb. 2, 2011.
He parted ways with Al Qaeda in 2012, after the jihadists seized most of northern Mali. He resurfaced as the spokesman of the Movement for Oneness and Jihad in West Africa, a separate jihadist group based in Mali, which merged with a third group in 2013.
Then in May 2015, he swore loyalty to the Islamic State leader, Abu Bakr al-Baghdadi. But his video pledge was not released by the group’s news agency for more than a year, until October 2016. Since then, Mr. Sahraoui’s statements have not been promoted on ISIS media outlets, including Friday’s claim, which was sent to the Mauritanian website. The Islamic State affiliate operating in Nigeria regularly succeeds in uploading messages and photo essays through established ISIS media channels.
That lack of a consistent media presence may suggest that Mr. Sahraoui’s unit has not been fully accepted by the Islamic State, or else that the group has not managed to establish the logistical ties that have allowed other affiliates to post statements and videos of attacks on its platforms.
In Bangladesh in 2016, for example, a relatively new affiliate was able to send images of an attack on a restaurant to the Islamic State’s Amaq News Agency before members of the security forces broke down the doors and ended the siege. Survivors later described how the attackers had demanded that employees turn on the restaurant’s wireless network so that they could send their images.
Similarly last June, the assailants who broke into Iran’s Parliament and the tomb of its revolutionary founder, managed to send a graphic, 24-second video to Amaq, showing them inside the building, walking past the dead and shouting Islamic State slogans.