At least four Nigerian military aircraft have been involved in deadly crashes since last year, including one that killed the nation's army chief and 10 other soldiers on board.

A Super Mushshak trainer went down on a military base on Tuesday evening, killing the two pilots on board, the air force said in a statement.

It said airforce chief Oladayo Amao had set up an investigation board "to determine the immediate and remote causes of the crash."

Soldiers are deployed in northwest and central Nigeria where they are battling heavily armed criminal gangs known locally as bandits.

Kaduna in particular, has been the epicentre of the attacks by the armed gangs.

Last month, a Nigerian passenger train was attacked with explosives, leaving eight dead and dozens kidnapped.

The attack on the train between the capital Abuja and Kaduna city was a major escalation in the security challenges wracking Africa's most populous nation of some 215 million people.

Nigerian troops are among other challenges also battling a 13-year-old jihadist insurgency in the northeast and a separatist agitation in the southeast.