Gunmen have kidnapped 140 children from a boarding school in north-western Nigeria, a school official has said, in the latest in a wave of mass abductions targeting schoolchildren and students. Heavily armed criminal gangs in north-west and central Nigeria often attack villages to loot, steal cattle and abduct people for ransom, but since the start of the year have increasingly targeted schools and colleges. The attackers opened fire and overpowered security guards after storming the Bethel Baptist high school in Kaduna state in the early hours of Monday, abducting most of the 165 pupils boarding there overnight. “The kidnappers took away 140 students, only 25 students escaped. We still have no idea where the students were taken,” said Emmanuel Paul, a teacher at the school. Parents and local people waited for news of the missing children outside the school, which hosts 185 pupils during the day. The Kaduna state police spokesperson, Muhammed Jalige, confirmed the attack but could not give details on the number of pupils taken. “Tactical police teams went after the kidnappers,” he said. “We are still on the rescue mission.” Police said they had safely rescued 26 people, including a teacher. About 1,000 students and pupils have been abducted in Nigeria since December. Most have been released after negotiations with local officials, although some are still being held. Often, gangs target rural schools and colleges where students stay in dormitories and security is light, allowing them to easily transport large numbers of victims to forest hideouts to negotiate ransoms. The kidnapping of Nigerian schoolchildren first made major international headlines in 2014 when the Islamist group Boko Haram snatched nearly 300 schoolgirls from a rural school in Chibok in the north-eastern Borno state, sparking the online  #BringBackOurGirls campaign. Recent abductions by gunmen have prompted six northern states to shut public schools to prevent such attacks. Bethel Baptist high school is a co-educational college established by the Baptist church in 1991 at the village of Maramara in the Chikun district outside the state capital, Kaduna. Monday’s attack was at least the fourth mass school kidnapping in Kaduna state since December. The Kaduna state governor, Nasir Ahmad El-Rufai, has been one of the most vocal local leaders on such attacks, insisting he will refuse to pay ransom money. Monday’s school abduction came just hours after gunmen snatched eight medical employees from a Kaduna health centre, according to police. “In terms of the number of attacks on schools, Kaduna has obviously suffered more than these other states,” said Nnamdi Obasi, an analyst with International Crisis Group thinktank. “The persistent targeting of schools in the state suggests the armed groups may be trying to break the state government’s resolve not to pay ransom to criminal groups.” Nigeria’s president, Muhammadu Buhari, a former general first elected in 2015, has promised to end the scourge of kidnapping and criminal gangs. But the mass abductions are only one challenge facing his government. His security forces have been battling an Islamist insurgency the north-east since 2009 – a conflict that has killed more than 40,000 people and displaced more than 2 million. The criminal gangs, known locally as “bandits”, operate from camps in the vast Rugu forest, which cuts across Zamfara, Katsina, and Kaduna states in Nigeria, as well as neighbouring Niger.