Some Syrians in the besieged areas of Daraya and Deir al-Zor have been reduced to eating grass because food supplies are cut off, the U.N. World Food Programme said on Friday.

“In the most severe cases, they are enduring entire days without eating, sending children to beg and eating grass/wild vegetation,” a report said.

Deir al-Zor is under seige by Islamic State (ISIS) forces, while Daraya is besieged by government forces and has become a focus of U.N. efforts to get aid to all of Syria. Syria’s government has not yet granted permission for aid to go to the city.

Households in the two cities were unable to eat more than one meal per day and giving priority to children, said the WFP report, a survey of Syrian food market conditions in February.

Fresh bread was “sporadically available at an extortionate cost” in Daraya, 30 times above the market price in nearby Damascus. Rice was 17 times higher than Damascus prices.

Despite a widespread truce that has lasted almost three weeks, Syria’s government has refused to give permission for U.N. aid convoys to enter six areas under siege by its forces, including Daraya.

U.N. humanitarian advisor Jan Egeland said on Thursday that countries backing the Syrian peace talks had given the Syrian government seven days to answer a U.N. request to deliver aid.

“It is in violation of international law to prevent us from going,” he said, adding that the six areas were no more strategic or symbolic than other areas that had already received aid convoys.

“In Daraya there has been fighting, but we had a very clear impression that we will not be having any problems in delivering if we get the two sides to agree to the cessation of hostilities so that we can deliver to the few thousand people there, civilians who are in a very, very difficult position,” Egeland said.

With no hope of getting convoys into Deir al-Zor by road, the U.N. hopes to do air drops of food. But a first attempt failed because the plane had to fly so high and fast to avoid the threat of surface-to-air missiles, causing the parachutes to fail because of the severe jolt when they opened.