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.
Russia and Ukraine completed the exchange of 1,000 prisoners each on Sunday, the Russian Defence Ministry and Ukrainian President Volodymyr Zelenskyy said, in the largest such swap since the war began three years ago.
Russian forces launched a barrage of 367 drones and missiles at Ukrainian cities overnight, including the capital Kyiv, in the largest aerial attack of the war so far, killing 13 people and injuring dozens more, officials said.
Russia and Ukraine each exchanged 307 of their service personnel on Saturday on the second day of a prisoner exchange that, when completed, is set to be the largest such swap in the three-year war between the two countries.
U.S. President Donald Trump has suggested the prisoner swap - which should see 1,000 prisoners released on each side over three days - could herald a new phase in stop-start efforts to negotiate a peace deal between Moscow and Kyiv.
Saturday's swap was announced by Russia's defence ministry, and separately by Ukrainian President Volodymyr Zelenskiy in a post on social
French police were investigating a possible arson attack as being the main cause for a power outage which hit the Alpes-Maritimes region in southern France on Saturday, including Cannes which is hosting its world-famous annual film festival.
Dubai’s Roads and Transport Authority (RTA) has announced the completion of 70 per cent of the Umm Suqeim Street Improvement Project, which extends from the intersection with Al Khail Road to the junction with Sheikh Mohammed Bin Zayed Road.
Abu Dhabi Police and the Civil Defence Authority have brought a fire under control that broke out at a store in the Mussafah industrial area on Sunday.
The World Silk Road Forum has named His Highness Sheikh Mohammed bin Rashid Al Maktoum, Vice President and Prime Minister of the UAE, and Ruler of Dubai, as the Inspirational Literary Figure for Silk Road Poets.
Russia and Ukraine complete largest prisoner swap
North Korea detains officials over warship accident
At least 13 killed in Russian air attack on Ukraine
Russia, Ukraine swap 307 soldiers on second day of POW exchange
Police probe arson attack in France power outage
