Hundreds of schoolgirls are feared to have been kidnapped in the north-western state of Zamfara.
A teacher told the BBC that at least 300 students were unaccounted for after the Friday morning attack by gunmen.
A spokesman for the state’s governor has confirmed the attack but did not give details.
This is the latest mass abduction targeting schools in recent weeks. Armed gangs often seize schoolchildren for ransom.
At least 42 people, including 27 students, who were kidnapped last week in the central state of Niger, are yet to be released.
In December, more than 300 boys were kidnapped by gunmen and later released after negotiations.
Friday’s attack happened at 01:00 local time (midnight GMT) when a group of gunmen arrived at the Government Girls Secondary School in Jangebe town with pick-up vehicles and motorcycles, a teacher told news site Punch.
Some of the gunmen were dressed as government security forces, the report said, adding that they forced the schoolgirls in the vehicles.
But other witnesses have told the BBC that the armed men arrived on foot at the school.
Worried parents have gathered outside the school and some have gone out into the bush to look for their daughters, witnesses say.
A teacher told the BBC that of 421 students in the school at the time, only 55 had been unaccounted for, meaning more than 300 were believed to have been kidnapped.