At least 78 students were kidnapped at Bamenda’s Presbyterian Secondary School in the capital of the north-west region of Cameroon on Monday.
The students were abducted along with their principal, a teacher and a driver.
Adolphe Lele L’Afrique, governor of the region, confirmed the incident, blaming it on militias.
Militias have been demanding the independence of the two English-speaking regions. They have called for a school boycott.
The kidnapping — the gravest incident so far in 13 months of unrest — coincides with an upsurge of political tensions in the majority French-speaking country.
It comes after elections on October 7 that saw President Paul Biya, 85, who has ruled the country with an iron fist for 35 years, secure a seventh term in office.
Cameroon’s North-West and South-West regions have been hit by a secessionist rebellion in recent years.
A video of some of the children, all boys, believed to have been filmed by one of the kidnappers, is being shared on social media.
The students, crammed into a tiny room, all look nervous as the person holding the camera orders them to say their names and where they are from.
They also repeat the phrase: “I was taken from school last night by the Amba boys, I don’t know where I am.”
Amba is short for Ambazonia, the name of the new country that the separatists want to create.
It is not the first time students have been abducted in the area, known to be a stronghold of separatist fighters.
On 19 October, five students of the Atiela Bilingual High School were taken by unidentified gunmen. Their whereabouts are still unknown.
The separatists say that the Cameroon school system suppresses the English-speaking system that the North-West and South-West regions inherited from the British.