Twin suicide car bombs exploded at a church inside one of Nigeria's top military bases, killing at least 11 people and wounding 30.
No group has claimed responsibility for the attacks in Jaji.
Suspicion has fallen on radical Islamist sect Boko Haram, whose suicide bombers have previously targeted Sunday worship services.
The attack in Jaji, however, happened inside a barracks home to the Armed Forces Command and Staff College, one of Nigeria's most important military colleges.
It also showed a new dangerous sophistication as the second explosion appeared timed to target responders rushing to aid the wounded ten minutes after the first blast, officials said.
The attack began just after noon and targeted the St Andrew Military Protestant Church, Brigade General Bola Koleoso said.
A bus loaded with explosives somehow made it inside the barracks' perimeter and rammed into the church's walls before exploding, Gen Koleoso said.
The second blast came from a sedan parked nearby and struck in the chaos afterward as emergency workers, soldiers and survivors of the first blast milled around the church.