The officer "went berserk...and opened fire killing 4 of his colleagues before shooting himself", in a base in Malam Fatori near the border with Niger, army spokesman Sagir Musa said in a statement late Wednesday.

Musa said two other soldiers injured in the incident were ferried to a military hospital in the regional capital Maiduguri, 205 kilometres (127 miles) away.

A military source said the soldier opened fire on his colleagues while they were on sentry duty at an observation post within the base.

"He killed four, injured two and shot himself in the head before he could be disarmed," said the military source, who asked not to be identified.

It was not immediately clear what led to the shooting but the army has opened an investigation to "determine the circumstances that led to the unfortunate incident", Musa said.

Nigerian troops fighting a decade-long Islamic insurgency in the northeast have complained of weariness after being in battle for so long without a break.

In August 2018, hundreds of soldiers protested at Maiduguri airport for several hours against a planned redeployment to fight the jihadists after four years at the front.

The soldiers shot into the air, disrupted flights and said they were tired and needed to see their families.

At least 36,000 people have been killed and around two million displaced from their homes since the start of the jihadist uprising in 2009.

The violence has spilled into neighbouring Niger, Chad and Cameroon, prompting a regional military coalition to fight the insurgents.