Armed men carried out the massacre on Friday in the village of Ntumbo in the Northwest Region, James Nunan, a local official with the UN’s humanitarian coordination agency OCHA, told AFP news agency.

According to the details, Eleven of the children were girls, said Nunan, head of OCHA’s office for the Northwest and Southwest regions, which are home to the West African country’s large English-speaking minority.

One eyewitness, who spoke to Al Jazeera on condition of anonymity fearing reprisals, confirmed the massacre and said he helped bury 21 bodies in “four graves in four different compounds” with the help of an associate.

Separatists in the regions have been fighting the central government for three years.

The Movement for the Rebirth of Cameroon, one of the country’s two main opposition parties, issued a statement saying: “The dictatorial regime (and) the supreme head of the security and defence forces are chiefly responsible for these crimes.”

A key figure in the separatist movement, lawyer Agbor Mballa, in a Facebook post also accused “state defence forces” of carrying out the killings.

An army official contacted by AFP early Sunday denied the allegations, saying simply: “False”. No other official response was immediately available.

The three-year conflict between anglophone forces seeking to break away from French-speaking Cameroon has claimed more than 3,000 lives and forced more than 700,000 people to flee their homes.