Six of the 136 students kidnapped from an Islamic school in the north-central Nigerian state of Niger have died of illness while in captivity.
The principal of their school Abubakar Garba Alhasan made the disclosure on Tuesday.
Alhassan told Reuters that the kidnappers had called to say the children died from sickness and to urge that the ransom demand be met.
Bandits attacked Salihu Tanko Islamic School in Tegina, Rafi local government area of Niger State on Sunday, May 30, 2021, and kidnapped 136 people, including three teachers.
They have since demanded a ransom to release the students.
Bandits and other criminal gangs have carried out a series of raids on boarding schools in northern Nigeria in which more than 1,000 students have been abducted since December.
Abubakar Adam, whose seven children are held by the gang, said the abductors called the principal to demand a ransom.
Kidnappers released 15 more students taken last month from a Baptist school in Kaduna State after parents paid an undisclosed ransom to free them.
Nigeria President Muhammadu Buhari in February said his government will be ruthless with terrorists, bandits, and other criminals.
Buhari advised state governments to stop paying ransom to kidnappers who he said use the funds to acquire more weapons.
Kaduna State governor Nasir Ahmad El-Rufai, whose state has been subjected to multiple attacks, killings, and abduction, also opposed the payment of ransom to kidnappers and bandits.
Parents of abducted students have accused the government of not doing enough to protect school children and help victims regain freedom.