Motorcycle gunmen opened fire on the car of a Nigerian air force officer on Sunday, killing the driver and an aide, while two other people were killed in a nearby neighbourhood, authorities said.
It was not clear who was behind the attacks in the city of Kano, the largest in Nigeria's mainly Muslim north, but they resembled similar killings in the past blamed on Islamist militant group Boko Haram.
"A car of one of our officers came under attack this morning," Air Commodore Sani Ahmed said.
"The officer's driver and his orderly were travelling out of town, but as they reached an area called Yan-Lemo, two gunmen on a motorcycle opened fire on the car, killing the two personnel."
The officer was not in the car at the time, he said.
In a similar incident earlier in the day, two gunmen on a motorcycle shot dead two people outside their house in a nearby neighourhood, said police spokesman Rilwanu Dutse.
A police source said the victims were from the mainly Christian Igbo ethnic group.
Boko Haram has carried out scores of bombings and shootings in their insurgency in the north of Africa's most populous nation that has left hundreds dead.© ANP/AFP