Nigeria's army chief, Lieutenant General Ibrahim Attahiru, died in an air force plane crash on Friday.
He was on an official visit to the northern state of Kaduna, which has had security challenges in recent months.
The air force said in a statement that its plane crashed near Kaduna airport and that it was investigating the cause.
The presidency added that other military officers were also killed in the crash.
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."
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 insurgents and armed gangs.
Thailand and Cambodia agreed on Saturday to halt weeks of fierce border clashes, the worst fighting in years between the Southeast Asian countries that has included fighter jets sorties, exchange of rocket fire and artillery barrages.
Malaysia's former premier Najib Razak was jailed on Friday for a further 15 years and fined $2.8 billion for power abuse and money laundering in the biggest trial of the multibillion-dollar 1MDB scandal, a ruling that could have big political ramifications.
The United States has carried out a strike against IS targets in northwest Nigeria at the request of Nigeria's government, President Donald Trump and the US military said on Thursday, claiming the group had been targeting Christians in the region.
Israel became the first country to formally recognise the self-declared Republic of Somaliland as an independent and sovereign state on Friday - a decision that could reshape regional dynamics and test Somalia’s long standing opposition to its secession.
The UAE's President His Highness Sheikh Mohamed bin Zayed Al Nahyan has held talks with Pakistan’s Prime Minister Shehbaz Sharif on strengthening cooperation between the two countries.