Nigerian gunmen on Wednesday kidnapped 73 pupils after storming a high school in the north-west of the country, police said.
Kidnappings for ransom by heavily armed gangs have become a grim trend in north-west and central Nigeria, with about 1,000 pupils taken this year, although most have been released after negotiations.
Police rescue teams were working with the military for the release of the Kaya secondary school pupils, police said.
North-west and central states have long been troubled by retaliatory attacks and community raids between nomadic herders and local farmers who clash over water and land.
But violence has intensfied sharply with the emergence of large criminal gangs who steal cattle, raid and loot villages, and kidnap for ransom.
This year they have raided schools, seminaries and universities across the region, taking children and students into forest hideouts while they negotiate ransom payments.
Many pupils have been released after spending weeks or months in captivity, and dozens are still being held.
In Zamfara, 18 students were freed last week after they were kidnapped earlier in August from an agricultural college.
Gunmen last week also freed nearly 100 children taken from an Islamic seminary in May in north-west Niger state and 32 pupils taken from a Baptist school in Kaduna State in July.
President Muhammadu Buhari is under pressure over insecurity and the armed forces have launched raids and air strikes on bandit camps, but gunmen have kept up the attacks.