Unidentified attackers ambushed and looted numerous aid trucks with essential items for remote villages and refugees forced to flee their homes by fighting in the western Sudan region, the International Committee of the Red Cross said.
The international relief group said the attacks were denying help to people who lacked even the most basic necessities. The attacks had been carried out against a number of aid agencies and had not targetted the ICRC itself, a spokesman said.
"These attacks against humanitarian convoys are hampering the humanitarian activities that are taking place in Darfur," said ICRC spokesman Marco Jimenez, without giving further details of the attacks.
Robbery rather than politics seemed to be the main motive, he added. Tens of thousands have been killed and more than 2 million people have fled their homes in Darfur since a rebellion broke out in early 2003.
The Khartoum government is accused of arming nomadic Arab militia known as Janjaweed, who have waged a campaign of violence against non-Arab villagers, which the United States has called genocide. Khartoum denies supporting the Janjaweed.
Human rights activists say that the 2,000 African Union troops charged with monitoring the security situation in Darfur are insufficient to deter violence in the remote region.