It was not clear who was behind the attacks in the city of Kano, the largest in the mainly Muslim north, but they resembled similar incidents in the past blamed on Islamist militant group Boko Haram.
The deadliest occurred on Sunday night when gunmen opened fire in an area around a mosque while Muslims were observing Ramadan prayers and where a police team was already deployed to protect worshippers, a senior police official said.
Police and the attackers exchanged fire and one of the assailants was killed when his own explosive device went off.
Three other gunmen were shot dead by police, according to the official who spoke on condition of anonymity.
“The rest fled, abandoning their car and three motorcycles they came with,” the official said, adding that it was not clear whether police or the mosque was the target of the initial attack.
Earlier in the day, gunmen on a motorcycle opened fire on the car of a Nigerian air force officer, killing the driver and an aide, while two other people were killed in a nearby neighbourhood, authorities said.
“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.