At least 20 Nigerian university students were abducted by gunmen who ambushed their vehicles in the country’s north-central region, police said Friday.

The students were travelling to the south for a conference of medical students when they were ambushed in Benue state on Thursday evening, according to Benue police spokesperson Catherine Anene. The attack happened along Benue’s Otukpo road, a notorious hotspot for kidnappings.

Such kidnappings have become common in parts of northern Nigeria, where dozens of armed groups take advantage of limited security presence to carry out attacks in villages and along major roads.

Most victims are released only after the payment of ransoms that sometimes run into the thousands of dollars. The attacks have also forced many to abandon road trips.

The students kidnapped in Benue were from the University of Maiduguri and the University of Jos, both in northern Nigeria.

Their respective student groups condemned the attacks and urged authorities to secure their release.

It was not immediately clear what group that carried out the attack or where the captives were taken. The police did not provide any update about rescue efforts.

“We are devastated by this senseless act,” Ijabani Bajam, a student leader from the University of Maiduguri, said in a statement that called for the safe return of the students.