At least 14 children were among 22 people killed by armed men in the English-speaking region of Cameroon, a UN official said.
The UN's James Nunan said the attack happened in Ntumbo, a village in northwestern Cameroon on Friday.
Details of the violence emerged Sunday. Nunan told CNN that an unspecified number of residents were injured, including a pregnant woman. He added that at least 600 villagers have since fled the area.
Rignyu Solange, who comes from Ntumbo, said nine members of her family were killed when security forces searching for separatists burned many houses in the village.
"My sister and her family were killed in their sleep as the military torched houses because they suspected that separatist fighters were hiding in the village. I want the perpetrators of this act to be severely punished," Solange told CNN.
The death toll from Friday's attack has risen to 32, Cameroonian activist and human rights lawyer Felix Agbor Nkongho from the Centre for Human Rights and Democracy told CNN on Monday.
"The military officers responsible for these heinous crimes must be brought to justice," he said.
Cameroon army spokesman Atonfack Guemo disputed the figures, saying only a woman and four children were killed in the crossfire between security forces and the separatists during the attack.
He said a team of six soldiers engaged the separatist fighters in the area, killing seven of them. He added that the fighting continued into the night and fuel containers hit by gunfire exploded, causing a blaze that spread through homes.
"This caused the death of five persons; a woman and four children, contrary to social media reports," he said.
Separatists in English-speaking regions of Cameroon have been fighting with government forces and government-backed militias for several years.
Both sides stand accused of violence against civilians, which began in 2016 after residents in the country's Anglophone provinces, where 20 percent of Cameroon's population live, protested the government led by French speakers.
Some groups in the region have also been fighting for an independent nation.
The Anglophone conflict has internally displaced more than 670,000 people in affected areas, while 60,000 Cameroonians have fled escalating violence to neighboring Nigeria, according to UN estimates released this month.
"Since December there has been a surge in violence throughout the two anglophone regions of Cameroon with thousands of civilians displaced," Nunan said.
Friday's attack comes a month after a military court in Cameroon opened proceedings against seven soldiers accused of summarily executing women and children in a raid against Boko Haram insurgents.
Last year, US President Donald Trump removed the country from a trade program over alleged human rights violations by the Cameroon army.