Suicide attacks on three churches and reprisal violence that saw Christians target Muslims in northern Nigeria have killed at least 45 people and the toll could rise further, a rescue official said Monday.

"As at last night, around 10 pm, the death toll stood at 45," the rescue official said on condition of anonymity as he was not authorised to issue death tolls. "The death toll is expected to rise when we get updated."

The previous death toll stood at 36.

Bomb blasts struck three churches in northern Kaduna state in the space of an hour on Sunday, the latest in a string of such attacks that has threatened to ignite wider sectarian strife in Africa's most populous nation and largest oil producer.

After news of the blasts spread, Christian youths took to the main motorway that leads to the capital Abuja, attacking motorists who looked Muslim.

Christian mobs carrying machetes and clubs also prowled the streets of Kaduna city, the Red Cross said.

Officials put Kaduna state under a 24-hour curfew.

There was no claim of responsibility for the church bombings, but Islamist group Boko Haram has been blamed for many similar attacks.