According to the group, which coordinates aid across Sudan, the paramilitary militia Rapid Support Forces (RSF) had targeted the center of the city of al-Fashir with "four high-explosive rockets".
The city has seen fierce clashes as both sides fight to secure a last foothold in the large Darfur region.
Almost the entire region is now controlled by the RSF, which has been fighting against the regular army since mid-April 2023.
Last week, Sudan's army carried out one of its deadliest airstrikes against a market in northern Darfur, which is reported to have killed over 100 people.
The war in Sudan has killed tens of thousands of people and forced more than 11 million to flee. The UN calls the situation in Sudan one of the worst humanitarian disasters in living memory. Both sides are believed to have committed war crimes.
