The United Nations' arm dedicated to children said it "strongly condemns" the kidnapping at a Presbyterian school near the regional capital Bamenda late on Sunday.
The organisation said: "UNICEF strongly condemns the reported attack and calls for the immediate and unconditional release of all the children abducted.
"UNICEF is deeply concerned about these reported acts of violence. Attacks on schools are a violation of children's right and schools should be safe spaces and protected at all times.
"UNICEF is concerned by the escalation of the conflict in the North-West and South-West regions of Cameroon and calls on all parties to allow humanitarian access to people in need in the affected areas."
Today, at least 70 schoolchildren were abducted in #Cameroon's Anglophone region. This shows how the general population is paying the highest price, as violence continues to escalate. Release & return the schoolchildren immediately. https://t.co/uVURqnyXkM
— AmnestyInternational (@amnesty) November 5, 2018
A video posted on social media showed suspects kidnappers expressing support for a separatist movement which seeks to create an independent state in Cameroon's English-speaking regions.
One of the world's leading human rights organisations, Amnesty International said the incident marked a "chilling echo" of the 2014 kidnappings of the Chibok schoolgirls - many of whom are Christians - in Nigeria.
Samira Daoud, Amnesty International's West and Central Africa deputy regional director, said: "In a case with a chilling echo of the 2014 kidnappings of the Chibok schoolgirls in Nigeria, it is vital that Cameroon's government act swiftly and decisively to reunite these children with their loved ones.
"We express solidarity with the families of these children and demand that the Cameroon authorities do everything in their power to ensure all the pupils and school staff are freed unharmed."
We strongly condemn the reported attack on a school in North-West Cameroon and call for the immediate and unconditional release of all the children abducted. #ChildrenUnderAttack https://t.co/90SrkVlQvL
— UNICEF (@UNICEF) November 5, 2018
Conflict between separatists and military forces in Cameroon's Anglophone areas has intensified since 2016.
Last week, an American missionary was shot dead in Bamenda.