Among the dead were many civilians, with one eyewitness claiming children had been thrown alive onto fires.
Some 75 people died in fighting close to the country's northern border with Chad, an official with the African peacekeeping force said today.
The clashes pitted fighters from the former rebel Seleka coalition against members of the Fulani tribe, the source said on condition of anonymity.
The official added that the killings were carried out over a period of "several days" in an area patrolled by armed fighters from the Seleka rebels and the Fulani tribe.
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"They attacked nearly 10 villages around Markounda between Wednesday and Friday. They also attacked more than 40 villages near Paoua on the Chadian border," said the same source.
One anonymous source told AFP by phone that the death toll could rise.
One resident of Markounda, Yetina Isaac, described how rebels attacked by banging "doors, shooting the occupants and then setting houses on fire".
"The injured and helpless perished and burned alive, while the bodies of those already dead were also burnt."
Isaac added that she saw children being "thrown alive on the fire".
News of the deadly clashes in the north came as it was announced that almost 30 people were also killed in fighting in the Mala region, some 200 kilometres north of the capital Bangui.
The deaths there were a result of fighting between Seleka rebels and the Christian vigilante groups known as the anti-balaka, another official from the African peacekeeping force MISCA told AFP, with locals forced to flee to neighbouring areas.
"They kill, loot, rape and steal with impunity. There is no one to protect the population from their abuses. Even the Catholic Church in Mala was attacked and those seeking refuge inside were fired upon and had to flee," said Eric Ketegaza, one of those who fled Mala.