CAIRO (AP) — An aid convoy was hit by drone strikes Thursday, killing three people and wounding four aid workers as it traveled to cities in central Sudan’s Kordofan region, the epicenter of fighting between the army and its rival paramilitary forces, a local doctors group said.

Sudan Doctors Network, a group that monitors violence in Sudan, said on X late Thursday that the trucks were carrying food and humanitarian supplies to the city of Kadugli and the town of Dilling in South Kordofan when they were struck in the Kartala area by drones it said belonged to the Rapid Support Forces, or RSF. It was not immediately clear which aid organization the convoy was affiliated with.

The war between the RSF and the Sudanese military erupted into a full-blown war across the country in April 2023. So far, at least 40,000 people have been killed and 12 million displaced, according to the World Health Organization. Aid groups say the true war death toll could be many times higher, as the fighting in vast and remote areas impedes access.

Most recently, the fight has been centered in Kordofan, where aid groups and analysts report an increase in drone strikes that hampered aid operations and took a toll on civilians, despite the army saying it seized control and broke the siege of Kadugli and Dilling. At least 77 people were killed in various attacks in Kordofan due to drone warfare in February.

A U.N. convoy reached Dilling and Kadugli with aid for more than 130,000 people, the first major delivery in three months, United Nations agencies said Wednesday. However, aid workers are concerned about escalating violence.

Thursday’s strike on the aid convoy is the second such incident in less than a month, according to Sudan Doctors Network. Earlier this month, an attack hit a World Food Program aid convoy in North Kordofan.

On Thursday, a U.N. backed fact-finding mission determined in a report that evidence of crimes committed in late October by the RSF in el-Fasher, the capital city of North Darfur, showed “hallmarks of genocide.” Following the release of the report, The United States sanctioned three RSF commanders for their actions in el-Fasher, and called on the group to commit to an immediate ceasefire, the U.S. Treasury Department said.