The RSF has been fighting the Sudanese army in that area, one of the key frontlines of a civil war that has raged since April 2023.
The army has taken firm control of the centre and east of the country while the RSF is working to consolidate its control of western regions, including North Kordofan.
The Emergency Lawyers human rights group said in a statement on Monday that the RSF had attacked several villages on Saturday around the city of Bara, which the paramilitary controls.
In one village, Shag Alnom, more than 200 people were killed via arson or gunshot.
Looting raids of the other villages killed 38 civilians, they said, while dozens of others had gone missing.
The next day, the group said, the RSF attacked the village of Hilat Hamid killing 46 people, including pregnant women and children.
More than 3400 people were forced to flee, according to the United Nations.
"It has been proven that these targeted villages were completely empty of any military objectives, which makes clear the criminal nature of these crimes carried out in complete disregard of international humanitarian law," Emergency Lawyers said, placing the responsibility with RSF leadership.
The United States and human rights groups have accused the RSF of war crimes, crimes against humanity and genocide.
Its soldiers have carried out a series of violent looting raids in territory it has taken control of across the country.
The RSF leadership says it will bring those found responsible for such acts to justice.
Sudan's civil war has created the world's largest humanitarian crisis, driving more than half the population into hunger and spreading diseases including cholera across the country.
A global reduction in aid spending has stretched the humanitarian response.
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