Sudan has permitted four aid agencies expelled from the country in March to return to troubled Darfur, UN's humanitarian chief John Holmes has said.

The four, Care International, Save the Children, Mercy Corps, and Padco were among 13 other organisations expelled in March by the Sudanese government following the indictment of President Omar al-Bashir by the International Criminal Court (ICC) for war crimes. The aid groups were accused of spying for the ICC.

Holmes said Sudan had agreed to allow NGOs to go back to Darfur provided they registered under slightly changed names and logos adding that all the groups had the opportunity to seek readmission.

"That possibility is there for all the organisations which were expelled and some of them already have taken advantage of it. They now [have] new registrations and will be restarting their operations," he said.

Aid operation in Darfur is one of the world's largest, and the expulsions sparked fears of a new humanitarian disaster. However, a month ago, Holmes said the situation had not deteriorated as much as feared, and in many instances the gaps had been filled by the UN and the Sudanese Government.

According to UN estimates, 300,000 people have died and two million displaced in the six-year conflict in Darfur.