Nigeria’s top-ranking army commander Lieutenant General Ibrahim Attahiru died when his plane crashed in the country’s northern state of Kaduna Friday, according to Nigerian military officials.

The cause of the plane crash was blamed on “inclement weather” as the plane was landing at the Kaduna International Airport, the armed forces said in a statement adding that the crash “claimed the lives of 10 other officers including the crew.” The names of the other officers were not released.

Army spokesman Brigadier General Mohammed Yerima said more details of the crash would be released soon.

This is the third air crash by Nigerian aircraft this year. 

Attahiru was reportedly visiting the restive Kaduna state. He’d only been appointed to the position in January.

His appointment was part of a large army shake-up to deal with the decade-long Boko Haram insurgency which has placed Nigerian President Muhammadu Buhari under political pressure.

Buhari, in a released statement on Twitter, described the crash as a “mortal blow to our underbelly at a time our armed forces are poised to end the security challenges facing the country.”

“We join Nigerians in mourning the tragic loss of life from today’s plane crash. The death of the Chief of @HQNigerianArmy Staff, Lt. Gen Ibrahim Attahiru is a tremendous loss to Nigeria. During this difficult time across Nigeria when security and peace [are] so needed, we offer our deepest sympathy to the family of General Attahiru and to the families of all those who perished,” the U.S. said.

Boko Haram, and since 2016 an Islamic State-affiliated splinter faction, the Islamic State’s West Africa Province (ISWAP), have waged an insurgency estimated to have displaced about two million people and killed more than 40,000.

In 2015, the leader of Boko Haram, Abubakar Shekau, pledged his allegiance to ISIS only to split from it a year later. The split was due to religious and ideological disagreements over the killing of civilians by Boko Haram, to which Shekau objected.

The Nigerian military has also been accused of committing numerous human rights violations.

The two terrorist groups want to create states based on their extreme interpretation of Islamic sharia law. Boko Haram, whose name roughly translates to “Western culture is forbidden” has been resilient during the conflict despite suffering heavy losses. It operates mainly in the Lake Chad Basin.

The Nigerian military is investigating intelligence reports saying that Shekau was either seriously wounded or killed while fighting ISWAP forces. But Shekau, like his organization, has been remarkably resilient. He’s been reportedly killed on many occasions by the military, only to reappear in later videos of the group.

“It’s a rumor. We are investigating it. We can only say something if we confirm it,” said Nigerian Army spokesman Mohammed Yerima regarding Shekau’s death.