Kano  - A Nigerian military court on Friday sentenced a soldier to death for killing five civilians rescued from Boko Haram.

The soldier, Lance Corporal John Godwin, was convicted by the General Court Martial in Maiduguri, capital of Borno State for killing the civilians in Yamteke town.

"The civilians were earlier rescued by troops of the soldier's battalion and were taken for investigation at the time the soldier shot and killed five of them," army spokesperson Kinsley Mfon Samuel said in a statement.

He said other soldiers were also handed jail sentences for offences ranging from manslaughter to illegal possession of firearms and ammunition.

"Sergeant Innocent Ototo was sentenced to life imprisonment for manslaughter after torturing and killing a 13-year-old boy who he said stole his phone," he said, adding that the incident happened at Zamanbari area of Maiduguri.

He said Lance Corporal Benjamin Osage and Private Sunday Onwe were sentenced to 20 years imprisonment each for manslaughter and illegal possession of firearms and ammunition.

The offences ran against the Nigerian Army's Rules of Engagement as well as the Geneva Conventions to which Nigeria is a signatory.

The army did not say exactly when the offences were committed.

In June a soldier was sentenced to death for killing a Boko Haram suspect.

Human rights groups have repeatedly accused Nigeria's military of a catalogue of abuses against civilians in the conflict with Boko Haram, including arbitrary arrest, torture and extrajudicial killing.

Thousands of people have been rounded up and held for long periods without charge on suspicion of links to the Islamist militants, whose insurgency has killed at least 20 000 since 2009.

Nigeria's civilian and Islamic courts retain capital punishment but the sentences are rarely carried out.