President Goodluck Jonathan described the assault as "the creation of the devil" and suggested it might be time to change tactics against the rebels, without going into details.

"They started gathering students into groups outside, then they opened fire and killed one group and then moved onto the next group and killed them. It was so terrible," said one surviving student Idris, who would only give his first name.

"They came with guns around 1 am (9am AEST) and went directly to the male hostel and opened fire on them ... The college is in the bush so the other students were running around helplessly as guns went off and some of them were shot down," said Ahmed Gujunba, a taxi driver who lives by the college.

Bodies were recovered from dormitories, classrooms and outside in the undergrowth on Sunday, a member of staff at the college told Reuters, asking not to be named.

Boko Haram and spin-off Islamist groups like the al-Qaeda-linked Ansaru have become the biggest security threat in Africa's second largest economy and top oil exporter.