Gunmen killed 10 Nigerian soldiers and an officer in central Benue state, the army said on Friday.
It was not immediately clear who was behind the attack but Benue is part of Nigeria's middle belt region, where gangs have taken up arms after years of communal clashes between herders and farmers.
"Nigerian Army troops operating in Benue State came under attack while on routine operational task," army spokesman Mohammed Yerima said in a statement.
The violence in the region marked the latest bout of instability in Nigeria, Africa's most-populous nation.
On Monday, heavily armed gunman freed more than 1,800 prisoners in the southeast, while armed gangs have kidnapped hundreds of school children in the northwest in recent months and militants in the northeast have waged a decade-long insurgency.
