As many as 22 villagers, including 14 children, were found dead in the anglophone area of Cameroon, the United Nations said, with an opposition party blaming the killings on the army.

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.

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"Up to 22 civilians were killed, including a pregnant woman," Nunan said, adding 14 children - including nine under age five - were among the dead.

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.

Nine houses were also set ablaze and an unknown number of villagers displaced, the witness said.

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

One of the country's two main opposition parties, the Movement for the Rebirth of Cameroon (MRC), 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 denied the allegations saying simply: "False." No other official comment was immediately available.

"Those responsible for these heinous crimes must be brought to justice. This culture of impunity must stop," Felix Agbor Balla, director of the Centre for Human Rights and Democracy in Africa, said in a tweet on Monday.

Thousands dead

Conflict between Cameroon's army and English-speaking fighters seeking to form a breakaway state called Ambazonia began after the government cracked down violently on peaceful protesters complaining of being marginalised by the French-speaking majority.

The conflict has forced half a million people to flee and presented President Paul Biya with his biggest threat in nearly 40 years of rule.

The three-year conflict has claimed more than 3,000 lives and forced more than 700,000 people to flee their homes.

Friday's killings followed elections on February 9 that were marred by violence in the regions blamed both on separatists and security forces.

Armed separatists prevented people from voting by threatening reprisals, while government soldiers were a heavy presence.

Separatists kidnapped more than 100 people and torched properties in the run-up to the elections, said Human Rights Watch (HRW).

The MRC refused to field a single candidate after its leader, Maurice Kamto, who spent nine months in jail after his defeat in 2018 presidential elections and is now overseas, called for a boycott of this month's election.

The government has not yet announced the results of the elections or turnout figures.