Nigerian President Bola Ahmed Tinubu on Friday sent troops to rescue more than 250 pupils kidnapped by gunmen from a school in the country's northwest in one of the largest mass abductions in three years.

The Kaduna state attack was the second mass kidnapping in a week in Africa's most populous country, where heavily armed criminal gangs on motorbikes target victims in villages and schools and along highways in the hunt for ransom payments.

Local government officials in Kaduna state confirmed the kidnapping attack on Thursday, but did not provide figures as they said they were still working out how many children had been abducted.

At least one person was shot dead during the attack, local residents said.

Sani Abdullahi, a teacher at the GSS Kuriga school in Chikun district, said staff managed to escape with many students when the gunmen, referred to by locals as "bandits", attacked early Thursday firing in the air.

He told local officials that 187 pupils had been snatched from the main junior school along with another 100 from primary classes. Three residents also said between 200 and 280 children and teachers had been snatched.

"Early in the morning... we heard gunshots from bandits. Before we knew it, they had gathered up the children," resident Musa Mohammed told AFP.

"We are pleading to the government, all of us are pleading, they should please help us with security."

The Kaduna abduction and the mass kidnapping a week ago from camps for people displaced by jihadists in northeast Borno state illustrate the challenge facing Tinubu, who promised to make Nigeria safer and bring in more foreign investment.

"I have received briefing from security chiefs on the two incidents, and I am confident that the victims will be rescued," Tinubu said in a statement ordering armed forces to track down the kidnappers.

"Nothing else is acceptable to me and the waiting family members of these abducted citizens. Justice will be decisively administered."

The two mass kidnappings came almost 10 years after Boko Haram militants triggered a huge international outcry in April 2014 by kidnapping more than 250 schoolgirls from Chibok in Borno state.

Some of those girls are still missing.

More than 100 people were reported missing after last week's mass kidnapping in Borno, but conflicting accounts have emerged about the time and number of victims.

- 'No stone unturned' -

Police did not provide figures for the Kuriga school kidnapping. But the numbers of those reported abducted in Nigeria are often lowered after people who went missing while fleeing attacks return home.

"The Kaduna State Government and Security Agencies are working round the clock to ensure the safe return of the school children," state governor Uba Sani said on social media platform X.

"I have received strong assurances from the President and National Security Adviser that no stone will be left unturned to bring back the children."

In the last three years, hundreds of schoolchildren and college students have been kidnapped in mass abductions in the northwest and central region, including in Kaduna.

Almost all were released for ransom payments after weeks or months spent in captivity at bandit camps hidden in the forests that stretch across northwestern states.

US Secretary of State Antony Blinken on Friday condemned the kidnappings in Kaduna as "reprehensible" in a post on X, adding that those "responsible for these horrifying attacks must be held accountable".

UN child welfare agency UNICEF also condemned Thursday's attack and called on the government to do more to protect students.

"Schools are supposed to be sanctuaries of learning and growth, not sites of fear and violence," UNICEF Nigeria director Cristian Munduate said in a statement.

Nigeria's armed forces are fighting on several fronts, including against armed criminals in the northwest and a long-running jihadist insurgency in the northeast that has killed 40,000 and displaced more than two million since 2009.

Fighting in Borno has eased as militants have been pushed back from the territory they once controlled, but they still carry out attacks, kidnappings and raids in remote areas.

Last September, gunmen abducted more than 30 people, including 24 female students, in a raid around a university in northwest Zamfara State.

In February 2021, bandits raided a girls' boarding school in the town of Jangebe in Zamfara, kidnapping around 300 students.

Months earlier, gunmen snatched more than 300 students from a boys school in Kankara in Katsina state before releasing them days later.

Between July 2022 and June 2023, 3,620 people were abducted in 582 kidnap-related incidents in Nigeria, according to local risk analysts SBM Intelligence. It has recorded 4,777 people abducted since Tinubu took office in May last year.