Nigeria’s army chief, Lieutenant General Ibrahim Attahiru, died in a plane crash on Friday on an official visit to the northern state of Kaduna, which has had security challenges in recent months, the presidency said.

The air force said in a statement that its plane crashed near Kaduna airport and that it was investigating the cause.

The presidency said the army general and other military officers died in the crash on Friday.

President Muhammadu Buhari, in a presidency statement, described the crash as a “mortal blow … at a time our armed forces are poised to end the security challenges facing the country.”

The crash occurred three months after a small Nigerian air force passenger plane went down just outside Abuja airport following alleged engine failure, killing all seven people on board.

Nigeria, Africa’s most populous nation, has had poor air safety record in the past, although it has improved in recent years.

Buhari appointed Attahiru alongside other military chiefs in January after years of mounting criticism over spreading violence by Islamist insurgents and armed gangs.

Boko Haram and its offshoot, Islamic State West Africa Province, have waged a decade-long insurgency estimated to have displaced about 2 million people and killed more than 30,000. They want to create states based on their extreme interpretation of Islamic sharia law.