KAMPALA, Uganda (AP) — Amnesty International says rich countries have failed in their obligation to help Uganda support thousands of refugees fleeing violence in South Sudan.

Muthoni Wanyeki, an Amnesty official in East Africa, said in a statement that Uganda is under "incredible strain as funds dry up and thousands continue to cross from South Sudan every day."

Amnesty urged donors, including the United States, to ramp up refugee support, saying it had spoken to refugees and aid agencies who spoke of a desperate lack of food, water, shelter and other basic services.

Over 900,000 refugees from South Sudan are sheltering in Uganda.

Ahead of a United Nations-backed summit here aimed at raising awareness of the refugee crisis, Uganda said it needs $2 billion to look after the refugees and host communities.