The Christian Association of Nigeria on Saturday increased its estimate of the number of students and teachers abducted from a Catholic school on Friday to 315 from an earlier estimate of 227.
The association said a verification exercise had found that a further 88 students had been captured after they tried to escape.
"This now makes it 303 students (and) ... 12 teachers, bringing the total number of abducted persons to 315," it said in a statement.
Nigeria's security situation has been under heightened scrutiny since US President Donald Trump threatened military action in the West African country over the treatment of Christians.
Nigeria's government says Trump's claims that Christians face persecution in Nigeria are a misrepresentation of the country's complex security challenges.
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