Theft of fuel from a World Food Programme (WFP) warehouse in Ethiopia’s Tigray will jeopardize humanitarian operations for people who desperately need assistance, said a UN spokesman on Thursday.

“It is now the lean season, and we are highly concerned about the impact this might have on malnutrition rates and food insecurity in the region,” said Stephane Dujarric, chief spokesman for UN Secretary-General Antonio Guterres.

Rebel forces in Tigray on Wednesday overpowered staff at the WFP warehouse in the regional capital of Mekelle and looted 12 tankers carrying 570,000 liters of fuel destined for aid distribution trucks.

An estimated 2 million liters of fuel is required every month for humanitarian operations. Prior to the arrival of these latest tankers, only 1.8 million liters of fuel had been brought into Tigray since April by the only open road into Mekelle, said the spokesman.

Wednesday’s looting occurred in the context of the resumption of fighting in Tigray between government forces and the Tigrayan People’s Liberation Front.

“We reiterate our concern for civilians who are in front-line areas and call on all parties to adhere to their obligations under international humanitarian law to ensure their protection,” Dujarric said. “We also renew our call on all parties to uphold their obligations under international humanitarian law and to respect humanitarian personnel, activities, assets and goods.”