Three Red Cross workers were killed and two wounded on Thursday when artillery fire struck a frontline aid distribution site in Ukraine on Thursday, the organization said.

The International Committee of the Red Cross workers were preparing to distribute wood and coal briquettes in the village of Viroliubivka, in the Donetsk region, when they were hit, the group said in a statement.

The aid distribution had not yet started and no residents were harmed, the Red Cross said. The supplies were intended to prepare residents for the cold winter nights that are soon to come.

The Red Cross said that its teams worked in the region regularly and that its vehicles were clearly marked.

Images from after the attack show a white truck with a large red cross centered on the side engulfed in flames, its cab on fire and plumes of black smoke billowing upward in an arch.

The wounded staff members were taken to receive medical attention, and one was in serious condition, the Prosecutor General’s Office of Ukraine said in a statement.