CAIRO, Nov 12 (Reuters) - About 750 Sudanese exiles went on hunger strike outside U.N. offices in Cairo on Saturday to back demands to receive assistance, rather than be repatriated.

The strikers were among about 1,500 Sudanese who have camped for over a month near the U.N. High Commissioner for Refugees (UNHCR) office in the Egyptian capital's affluent Mohendiseen district.

"We started a hunger strike so the U.N. will hear our demands. We demand to stay here, and not be returned to Sudan. We want them to help us with health and security," said Mohamed Hussein, 31, a student from Darfur in western Sudan.

Clothes lines criss-crossed the camp, in which Sudanese of all ages sat among heaps of blankets and rubbish. They said five people, including three children, had died in the camp and that many suffered from malnutrition and disease.

The UNHCR said in a statement that Sudanese in Egypt were generally not fleeing persecution or violence, but were economic migrants hoping for resettlement in the West.

"UNHCR considers that the situation of most Sudanese present in or coming to Egypt today should be approached primarily as an economic migration and development challenge," it said.

Fighting between mostly non-Arab rebels and Sudan's Islamist government has forced two million people from their homes in Darfur and left tens of thousands dead since early 2003.

The protesters said those in the camp were not all from Darfur and some had fled Sudan before the Darfur troubles began. They complained of discrimination and ill-treatment in Egypt.

"The UN has been saying it will help us for a long time, but it doesn't. There are racists and thugs who attack us and the police don't do a thing. Some Egyptians ... have taken advantage of Sudanese women," said Bahel Eldin Adam, 35, also from Darfur.

The UNHCR said it was not in its power to solve underlying issues of discrimination and deprivation, and that having left Sudan, economic migrants try to pass themselves off as refugees from Darfur to gain easier passage to richer nations.

The agency targets those genuinely facing violence and human rights abuses. It said it had resettled 17,000 Sudanese refugees in Egypt or in Western countries in the last seven years.