GENEVA -- A UN-appointed official dealing with hunger on Monday condemned U.S. airdrops of food rations in Afghanistan as a catastrophe for humanitarian aid and warned that the U.S. was effectively feeding Taleban fighters.

Jean Ziegler, UN special rapporteur on the right to food, said the airdrops of food by the same military force dropping bombs on Afghanistan undermined the credibility of humanitarian aid.

He said aid deliveries needed to be supervised on the ground.

"As special rapporteur I must condemn with the last ounce of energy this operation called snowdropping, it is totally catastrophic for humanitarian aid, for all the extraordinary work that UN agencies and International Committee of the Red Cross (ICRC) and Medecins Sans Frontieres (MSF: doctors without borders) are doing," Ziegler told journalists.

U.S. military transport aircraft have been dropping thousands of rations over Afghanistan, while separate bombing raids continue, amid warnings that millions of Afghans are short of food.

The practice is known in the humanitarian community as "snowdropping" because it scatters individual packages over a relatively wide area.

Ziegler, who was appointed by the UN Human Rights Commission to examine the impact of hunger on human rights, said: "If there is no one to receive it on the ground, to distribute or to do the humanitarian work, it's obvious that the man with the gun picks it up. So Americans are feeding the Taleban every night," he added.

The Taleban authorities asked foreign relief workers to leave Afghanistan four weeks ago. Some supply convoys have been able to get into the country by road, but relief agencies say they have been severely hampered by the security situation, including the bombings by U.S.-led forces.

"It's true that airdrops of food are carried out in the world, but those are operations where the reception on the ground is guaranteed by the UN or the International Committee of the Red Cross, in other words by those who carry out the airdrop," Ziegler said

Many relief agencies regard the practice of "snowdropping" as a last resort.

"For us it's when nothing else works," Christiane Berthiaume, spokeswoman for the World Food Program (WFP) said.

Ziegler said there was added danger around the main cities in Afghanistan where landmines laid during 20 years of civil war are concentrated, especially for children.

"There's no ground perimeter (for airdrops), there's an extraordinary danger from landmines," he added.

Relief agencies say about seven million people in Afghanistan are dependent on outside food and medical supplies and they urgently need to step up deliveries before the onset of winter in the middle of November.