The bombing on Sunday hit St Andrew Military Protestant Church at the Armed Forces Command and Staff College (AFCSC).
Initially authorities said 11 persons were killed and later military spokesman Brig Gen Bola Koleoso said the number has gone up to 15.
But the hospital official at a military hospital in Kaduna said security has been tightened to restrict outflow of information.
He said the new deaths were among the thirty persons formerly injured after the attack and taken to the hospital for treatment.
An officer described the incident as embarrassing because the bombers drove their way into a military cantonment without being detected.