Kampala — Rebels are killing, looting and burning huts across northern Uganda, threatening to plunge up to half a million people into starvation, U.N. officials have said.

Lord's Resistance Army (LRA) rebels have blazed a trail of carnage since June, hacking dozens of people to death and disrupting farming in a land perched on a knife-edge between survival and starvation. They have also kidnapped thousands of children.

U.N. workers fear the latest rebel havoc will hit the vital December-January harvest, forcing them to triple the amount of aid they give to 500,000 people forced to flee during the 16-year insurgency.

"If the security situation continues like this, with farmers not accessing their fields, then we are going to face a very big food crisis," said Fred Olaa, the local head of distribution for the U.N.'s emergency food aid arm, the World Food Programme.

"It's the rebels who are making most places inaccessible," he said, as thousands of villagers clamoured for sacks of beans delivered by aid trucks on Monday to Anaka, a large cluster of mud huts lying deep in the bush.

Hungry children, their bellies swollen like balloons due to malnutrition, waited patiently with their mothers for the rations, the monthly highlight for inhabitants too scared of the rebels to farm.

The rebels have abducted over 20,000 children, brainwashing them into fighters or sex slaves.