The activist group Emergency Lawyers said in a statement that more than 100 people were killed when Sudanese government forces attacked a market full of civilians in North Darfur on Monday.
Several children are said to be among those killed.
The attack and the death toll have not been independently confirmed. The government army denies being behind the attack.
Sudan has been ravaged by civil war since April last year. Tens of millions suffer from acute food shortages. More than 14 million are displaced.
The conflict is between government forces and the paramilitary group RSF, both of whom are accused of committing gross human rights violations during the war.