Nigerian authorities are searching for hundreds of schoolgirls who were kidnapped by gunmen in a raid early Friday morning, according to police in the northwestern state of Zamfara.

Police Commissioner Abutu Yaro told reporters that 317 girls had been kidnapped from Government Girls Science Secondary School in the town of Jangebe, according to its principal. He said that efforts to trace the kidnappers and retrieve the students are underway and that authorities were looking into information that they had been moved to neighboring forests.

“All of us are angry, and all of us are sad,” he said. “Despite that we need to have a coordinated response in order to [save lives] and bring the children back home.”

Yaro emphasized the importance of exercising caution and care, and urged people to remain calm. According to local media reports, scores of residents incensed by the abduction stormed the streets of Jangebe, creating roadblocks and using sticks and stones to attack vehicles carrying journalists to the school. A cameraman was injured in the process.

Citing a police spokesperson, Nigerian newspaper Punch reported that Zamfara State Police Command is working with the military to conduct joint search and rescue operations for the students, who he said were kidnapped by “armed bandits.”

An unnamed school staff member told the newspaper that the gunmen — some wearing uniforms and pretending to be security personnel — arrived at the school with pickup trucks and motorcycles around 1 a.m. on Friday then “broke into the students’ hostels” and “forcefully evacuated” them.

“When they came into the school, we thought they were security personnel, but to our utmost fear and dismay, they started putting the girls into Hilux vehicles and motorcycles then drove out of the school,” the staff member said.

The armed kidnappers fired sporadically during the raid, Zamfara’s information minister told Reuters.

It’s the latest in a string of abductions in northern Nigeria and comes just over a week after gunmen kidnapped 42 people at a boarding school in the north-central state of Niger in an attack that left one student dead. In December, the northwestern state of Katsina saw two mass kidnappings eight days apart.

In a statement issued Friday condemning the attack, UNICEF’s Nigeria representative Peter Hawkins acknowledged the Nigerian government’s efforts to secure the kidnapped students’ release and called on it “and all concerned” to make schools safer.

“This is a gross violation of children’s rights and a horrific experience for children to go through — one which could have long-lasting effects on their mental health and well-being,” he said.

Amnesty International called the abduction a “serious violation of international humanitarian law” that undermines the right to education for thousands of students in the region. It said the abducted students are at “serious risk of being harmed” and called on authorities to take all measures to ensure the girls’ safe return, along with that of all students still in the custody of armed groups.

Most notoriously, some 100 of the more than 270 schoolgirls abducted by militant Islamist group Boko Haram in 2014 are still missing.

“Education is under attack in northern Nigeria,” Amnesty International tweeted. “Schools should be places of safety, and no child should have to choose between their education and their life. Other children have had to abandon their education after being displaced by frequent violent attacks on their communities.”