The United Nation's incoming humanitarian head has warned of low morale among relief workers operating in the Darfur region of African Sudan.

John Holmes said that even one major security incident could instigate a "humanitarian collapse", which in turn could affect tens of thousands of refugees currently under the care of agencies in the region.

The new UN humanitarian chief is on a tour of Sudan, Chad and the Central African Republic, where he has stated that the hundreds of thousands of people displaced by the four-year conflict are feeling cut off, the BBC reports.

In January, aid agencies including World Vision and Oxfam International warned that the enormous humanitarian response in Darfur was in danger of soon being paralysed unless urgent action was taken to end rising violence against civilians and aid workers.

Currently many security road blocks are in place across the region, which has limited the access of aid agencies to deliver vital medical, food and water supplies.

In particular, the new UN humanitarian chief has said that morale among humanitarian staff is fragile at the best.

Holmes said, "I hope the fact that I'm new can enable me to make a bit of a new start with the Sudanese government here. That's what I'm trying to do. And if I can make some forward progress on that basis so much the better."