Oxfam GB, expelled from Sudan alongside several other NGOs in early March, has appealed against the decision, warning the humanitarian situation in Darfur had deteriorated since then.
Sudan expelled the NGOs soon after the International Criminal Court (ICC) indicted President Omar Al-Bashir for war crimes and crimes against humanity in the country's western Darfur region, where civil war has killed hundreds of thousands and displaced at least half a million people since 2003.
"We strongly refute the government's accusations that we have acted outside our humanitarian mandate," Penny Lawrence, Oxfam GB's international programmes director, said in a statement issued on 15 April.
Oxfam said it had still not been given an official reason why its registration was revoked.
"We have already been told that water pumps in some Darfur camps have stopped pumping, and there are growing fears about the potential for outbreaks of disease in the coming rainy season," Lawrence said. "The expulsion is already affecting the lives of hundreds of thousands of the very poorest and most vulnerable Sudanese people."
The appeal was submitted in the timeframe given under Sudanese law, the agency added.
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