The gunmen, who are yet to be identified, stormed the premises of Limawa Primary and Secondary School in Minna, the provincial capital, state police spokesman Ibrahim Gambari said.
The incident occurred at 10.30 a.m. as students settled in their classrooms for the day’s lessons, he said, adding normalcy had since returned to the area following intervention of security personnel.
A witness said apart from shooting sporadically, the gunmen used their machetes to inflict severe injuries on some of the students.
“This is why there are fears of a high number of casualties,” said the witness identified as Ismail Bello.
Monday’s attack occurred six days after a woman suicide bomber blew herself up at the Federal College of Education in Kontagora area of the same state.
Last Monday, a male suicide bomber wreaked havoc at a school in Potiskum town of northeast Yobe State, killing dozens of students and injuring even more.
Recent attacks in Nigeria are being blamed on the Boko Haram, a terror group which has proved to be a major security threat in Africa’s most populous country.
The violent attacks by the Boko Haram, spanning five years, have claimed thousands of lives, including those of women and children.