The United Nations says rising violence is jeopardizing relief operations in Sudan's Darfur region.

The U.N. Office for the Coordination of Humanitarian Affairs says more aid workers have been killed in the last two weeks than in the previous two years.

The agency says eight humanitarian aid workers died while on duty last month, and that aid workers report an increase in hijackings, looting, and ambushes on their vehicles.

U.N. humanitarian official Manuel da Silva says all sides in the Darfur conflict need to respect the neutrality of humanitarian workers.

Violence in Darfur continues despite a May 5 peace agreement between Sudan's government and largest of the region's rebel groups.

Chaotic fighting between rebel groups, the government and militias has killed some 200,000 people and displaced another two million from their homes.