The international aid agency Oxfam says it will have to pull out of Darfur in western Sudan if the situation gets any more dangerous.
Some 400,000 Darfuri refugees depend on international aid
One Oxfam staff member has been killed there this year. Some 100 aid workers have been hostage and nearly 100 vehicles hijacked over the same period.
Oxfam's humanitarian operation in Darfur is one of the agency's largest in the world, assisting 400,000 people.
Some 2m have fled and an estimated 200,000 have died during the conflict.
This year alone the organisation's budget for providing relief in Sudan's western region is about $12m.
But the outgoing country director Caroline Nursey is warning that if violence against aid workers continues to escalate, Oxfam may be forced to pull out.
Shootings and rapes
"There is only a certain amount that an organisation can tolerate, there is only a certain amount of risk."
One member of staff was killed last year - others have been assaulted, had guns pointed in their faces and had their vehicles carjacked.
"Aid workers have been raped. Aid workers have been killed. This is unacceptable," she said.
It is not just Oxfam that has been targeted - last week three aid workers from the organisation World Vision were shot - two of them in the head.
Many hope the situation on the ground will improve after peace talks due to take place next month in Libya.
But not all the rebel factions have signed up to take part and the US Deputy Secretary of State John Negroponte said measures could be taken against rebel leaders who refused to attend.
A day of talks on Darfur at the UN at the weekend ended with disagreement over the composition of the force and the suggestion that unresolved technical issues are holding up deployment of the estimated 26,000 troops due to be deployed by early 2008.