At least 13 people have been killed - eight of them children - after a drone strike on a house in the Sudanese city of el-Obeid, says the Sudan Doctors' Network.
Most of the dead were part of the same family, the medical group added.
Although no group has claimed responsibility, the medics say the paramilitary Rapid Support Forces (RSF) carried out the attack in an area controlled by the army, which it has been trying to penetrate for months.
As the civil war between Sudan's army and RSF rebels approaches its third year, the scale of suffering has been labeled the world's worst humanitarian crisis by the UN and various aid agencies.
To date, more than 11 million people have been forced from their homes due to the violence, with hundreds of thousands reported dead. Widespread sexual violence is also being deployed as a weapon of war.
Both the RSF and the Sudanese Armed Forces are accused of committing atrocities.
Witnesses say Monday's drone attack on the house in el-Obeid took place in a residential neighborhood.
The Sudan Doctors' Network describes the incident as reflecting a dangerous escalation in the policy of indiscriminate killing and systematic bombing of safe residential areas.
The city of el-Obeid remains under army control despite the RSF's advances in the greater state of North Kordofan.
Analysts consider it a strategic target for the RSF due to its location between Sudan's capital, Khartoum, and the Darfur region, where they have established a parallel government and are facing accusations of genocide.
The attack comes only days after the RSF targeted a power plant in el-Obeid and follows claims of an attempted RSF drone strike on Sudan's largest hydro-electric dam near the northern town of Merowe.
Additional reporting by Andrew Ochieng.
