The United Nations refugee agency on Monday said it expected over 1.8 million people from Sudan to arrive in five neighbouring countries by the end of the year and appealed for $1 billion (€926 million) to help them amid reports of rising disease and death rates.

The estimate for those fleeing violence is about double what UNHCR projected in May shortly after the conflict began and an increase of 600,000 from an interim estimate.

Already, more than 1 million people have left Sudan to neighbouring states of Chad, Egypt, Ethiopia, South Sudan and Central African Republic amid fighting between the Sudanese army and the paramilitary Rapid Support Forces (RSF) in the capital Khartoum and beyond.

Many are so-called returnees or people who are returning to countries from which they previously fled.

In South Sudan, which is due to receive a third of the 1.8 million people fleeing, thousands of people, many sick and exhausted after crossing the White Nile River, have been arriving in a transit centre, aid group Médecins Sans Frontières said.

Others have died on board the boats during the nearly three-day crossing, it said.

UNHCR voiced growing concern about the health of the new arrivals, reporting rising malnutrition rates and disease such as cholera and measles in “several” host countries.

“It is deeply distressing to receive reports of children dying from diseases that are entirely preventable, should partners have had sufficient resources,” said Mamadou Dian Balde, UNHCR regional refugee coordinator for the Sudan Situation. “Action can no longer be delayed.”

The revised appeal represents an increase of nearly half a million dollars and takes into account the additional refugees and the extension of programmes by an additional two months to the end of December, a spokesperson told Reuters. The new regional appeal is only 19% funded, he said.