The bomb exploded as the woman was about to enter a hall packed with
students at a college in Kontagora town, the witnesses added.
Casualties numbers are unclear, but lecturer Andrew Randa said on
hisTwitter account that he had seen at least three bodies.
Militant Islamist group Boko Haram is waging an insurgency in Nigeria.
The group has declared a caliphate, or Islamic state, in areas it
controls in north-east Nigeria.
It has carried out a spate of bombings and assassinations in
north-east and north-central Nigeria since launching its insurgency in
At least seven people were wounded by the suicide bombing and rushed
to hospital, witnesses told the BBC Hausa service.
The bomber died in the blast, the witnesses said.
The explosion caused a deafening sound, and panic-stricken students
and staff fled for safety, Mr Randa said.