The Nigeria Army has commenced a formal investigation after a soldier shot dead four colleagues on Wednesday before taking his own life, the army says.

According to reports, two other soldiers were injured in the incident at a military base in Borno state and were taken to a military hospital in Maiduguri for treatment, army spokesman Sagir Musa added.

A statement by the Acting Director, Army Public Relations, Col Sagir Musa, confirmed the incident:

"Two (2) of his colleagues were also injured during the incident and are currently in stable condition in our hospital in Maiduguri.

"Efforts are ongoing to contact the families of our gallant colleagues who paid the supreme price in the line of duty. May their gentle souls Rest In Peace.

"Meanwhile, investigation into the case has since been instituted to determine the circumstances that led to the unfortunate incident".[Vanguard]

Last year, a retired officer, who now specialises in mental health, said many soldiers fighting Boko Haram militants were "suffering mental illness in silence", BBC quoted a 2019 report by PRNigeria.