A rebel leader of the Sudan Liberation Army warned the main airport in the Darfur region was considered a viable target for his forces.
The U.N.-African Union hybrid peacekeeping mission in Darfur expressed alarm over the latest threats, saying its efforts could be undermined without air transport.
"The mission should like to emphasize that, owing to the region's geographic conditions and lack of infrastructure, most humanitarian relief such as food, water, shelter and medical supplies is transported by air," the mission said in a statement.
South Darfur Gov. Abdel Hamid Moussa Kasha last week charged French medical group Doctors of the World with sharing intelligence with the Sudan Liberation Movement and accused troops loyal to the government in Khartoum of sexual assault.
The aid group claims it's a humanitarian agency working to assist vulnerable populations in war-torn countries. Officials in Darfur, however, said the group was making false claims and undermining peace efforts.
International observers complained that the attention given to a January referendum for South Sudanese independence was overshadowing lingering conflict in Darfur, the site of one of the bloodiest campaigns of genocide.