More than 100,000 people have fled Sudan since heavy fighting broke out between rival forces on 15 April, the UN has said.
Officials warned of an "all-out catastrophe" if fighting does not end.
A further 334,000 people have been displaced within Sudan.
Fighting is continuing in the capital, Khartoum, between the army and the paramilitary Rapid Support Forces (RSF), despite a ceasefire due to be in force.