Adam Smigielski/iStockBy MORGAN WINSOR and JAMES BWALA, ABC News

(LONDON) -- Hundreds of students who were abducted from an all-girls boarding school in northwestern Nigeria last week have been released, authorities said Tuesday.

Gunmen kidnapped 317 students from the Government Girls Junior Secondary School (GGSS) in the rural town of Jangebe in Zamfara state before dawn on Friday, according to a statement from Mohammed Shehu, spokesperson for the Nigeria Police Force's Zamfara State Police Command. The incident -- the latest in a recent string of mass abductions of students in the West African nation -- caused international outrage, with the United States condemning the attack.

Zamfara state police and the Nigerian military have conducted joint operations to rescue the schoolgirls.

The governor of Zamfara state, Bello Matawalle, announced early Tuesday that 279 schoolgirls have been freed. The terms of their release were not immediately known. It's also unclear whether others remain in captivity, as the discrepancy in the numbers was not explained.

"It gladdens my heart to announce the release of the abducted students of GGSS Jangebe from captivity," Matawalle said in a statement posted on Twitter, along with photos of some of the girls. "This follows the scaling of several hurdles laid against our efforts. I enjoin all well-meaning Nigerians to rejoice with us as our daughters are now safe."

Nigerian President Muhammadu Buhari took to Twitter to express his "overwhelming joy" over the release of the schoolgirls.

"I join the affected families and the people of Zamfara State in welcoming and celebrating the release of the abducted students of GGSS Jangebe," Buhari tweeted. "This news bring overwhelming joy. I am pleased that their ordeal has come to a happy end without any incident."

"We are working hard to bring an end to these grim and heartbreaking incidents of kidnapping," he added. "The Military and the Police will continue to go after kidnappers. They need the support of local communities in terms of human intelligence that can help nip criminal plans in the bud."

Last week, in the wake of the abduction, Buhari warned that policies of paying ransoms to bandits have "the potential to backfire with disastrous consequences."

"We will not succumb to blackmail by bandits and criminals who target innocent school students in the expectation of huge ransom payments," he tweeted Friday.

Schools in rural Nigeria have been targeted in attacks and kidnappings in recent years. On Saturday, 27 students, five staff members and nine family members of the staff were freed more than a week after being taken from an all-boys boarding school in the west-central town of Kagara in Niger state. In December, 344 students were released about a week after being kidnapped from another boys' boarding school in the northwestern town of Kankara in Katsina state. The Nigerian government has said no ransom was paid for their release and, in both cases, authorities blamed the attacks on armed groups, locally called bandits, who are known to abduct students for money in many Nigerian states.

One of the most well-known kidnappings was in April 2014, when members of the jihadist group Boko Haram snatched 276 students from their dormitory at an all-girls boarding school in the northeastern town of Chibok in Borno state. Some of the girls managed to escape on their own, while others were later rescued or freed following negotiations. But the fate of dozens remains unknown.

Boko Haram, whose name in the local Hausa language roughly translates to "Western education is forbidden," has waged an Islamist insurgency in northeastern Nigeria since 2009 and has been targeting schools for a number of years, with the Chibok attack being the most notorious and widely publicized. The group's uprising was fueled largely through the its systematic campaign of abducting children and forcing thousands of girls and boys into their ranks, according to a 2017 report by the United Nations International Children's Emergency Fund (UNICEF). A faction of Boko Haram has been aligned with ISIS since 2015.

In a statement Saturday reacting to the news that the Kankara students were freed, UNICEF Nigeria representative Peter Hawkins lamented that children are victims of attacks on their schools "far too often in Nigeria."

"Such attacks not only negate the right of children to an education, they also make children fearful of going to school, and parents afraid to send their children to school," Hawkins said. "Schools must be safe places to study and develop, and learning should not become a perilous endeavour.”

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