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

The four groups - named as Care International, Save the Children, Mercy Corps, and Padco - were among 13 organisations expelled in March.

However, Sudanese officials have strongly denied the reports.

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

However, Sudanese Foreign Ministry spokesman Ali al-Sadiq said this week that expelled aid agencies "will not come back to Sudan under their previous names or new ones", reports the state-run Suna news agency.

Sudan's UN Envoy Abdel-Haleem also denied the claims, telling Voice of America radio:

The Sudanese government expelled the aid groups in March, following the announcement that President Omar al-Bashir was being indicted by the International Criminal Court (ICC) for war crimes in Darfur.

The aid groups were accused of spying for the ICC - claims they strongly denied.

The aid operation in Darfur is one of the world's largest, and the expulsions sparked fears of a new humanitarian disaster.