Humanitarian food supplies in Yemen - where up to 20 million people are facing famine - are being stolen and sold for profit in the capital Sanaa and other areas of the country under Houthi rebel control, the UN said, urging an end to the "criminal" practice.
"This conduct amounts to the stealing of food from the mouths of hungry people," said UN World Food Programme Executive Director David Beasley.
"At a time when children are dying in Yemen because they haven't enough food to eat, that is an outrage. This criminal behaviour must stop immediately," Beasley said.
Shockingly, food aid was misappropriated by at least one local WFP partner organisation, which is affiliated with the de facto Ministry of Education in Houthi-controlled Sanaa, according to checks carried out in recent months, the UN agency said.
WFP began an investigation after a growing number of reports of humanitarian food for sale on the open market in the capital, the agency said.
And a survey of registered beneficiaries revealed that many needy people in the capital have not been receiving the food rations to which they are entitled, the agency said.
In other areas of civil-war-wracked Yemen, where most of the population relies on food assistance to survive, hungry people have been denied their full rations, according to WFP.
During their checks, WFP monitors amassed photographic and other evidence of trucks illicitly removing food from designated food distribution centres.
The monitors also found that local officials were giving food aid to people not entitled to it and that food distribution records were being falsified,
As food becomes increasingly scarce in Yemen, WFP said it is ramping up its food relief operations to reach as many as 12 million severely hungry people in the country.
"I'm asking the Houthi authorities in Sanaa to take immediate action to end the diversion of food assistance and ensure that it reaches those people who rely on it to stay alive," Beasley said.
"Unless this happens, we'll have no option but to cease working with those who've been conspiring to deprive large numbers of vulnerable people of the food on which they depend," he stated.
WFP is continuing to probe the scandal and to address the weaknesses of the food relief system that has been allowing the misuse of aid to take place, Beasley noted.
But de facto authorities in Houthi-controlled areas of Yemen have resisted WFP efforts to overhaul the current system by more monitoring, reform of the beneficiary selection process to make sure that food gets to the neediest and the nationwide introduction of biometric registration of beneficiaries, the agency said.
On a positive note, withdrawal of Houthi troops from Yemen's strategic port of Hodeidah, which began last week under a UN-brokered ceasefire, should allow more food to enter Yemen, WFP noted.
There are now "real hopes" of an end to Yemen's devastating civil war which began in 2015, WFP said, while urging combatants and local officials to ensure that crucial food supplies reach those who need them most.
More than 22 million people - three-quarters of Yemen's population - currently depend on humanitarian assistance to survive.