From the BBC, has more of the latest development on Darfur.
Sudan expelled 13 foreign aid groups in March after the International Criminal Court (ICC) issued an arrest warrant for Sudanese President Omar al-Bashir.
Meanwhile, the backer of a conference on Darfur says it has been cancelled because of opposition from Sudan.
It was intended to bring together some 400 people from Darfur's diverse ethnic groups in the Ethiopian capital, Addis Ababa.
Pro-government groups as well as those close to Darfuri rebels were included.
Funded by Sudanese expatriate and telecoms entrepreneur Mo Ibrahim, it also had the backing of the UN, the African Union and the Arab League.
"The Sudanese government is obstructing the safe passage of Darfurian delegates from Sudan, forcing us to cancel the conference," his foundation said.
Mr Ibrahim told the BBC delegates had being harassed, their passports withdrawn and that some had been warned they were engaging in activities against the state.
BBC Africa analyst Martin Plaut says work to prepare for the conference has been under way for nearly a year, and UN planes and helicopters had been on standby to help airlift the delegates to Ethiopia.
The UN says that up to 300,000 people have died during the conflict in Darfur and 2.7 million been driven from their homes.