The number of people uprooted by the war between rival generals in Sudan is around eight million, the United Nations said on Wednesday.
UN High Commissioner for Refugees Filippo Grandi, who is visiting Ethiopia, rallied international donors to open their wallets to fight the crisis, describing the situation as "serious".
"The conflict has increased in intensity and in impact on civilians," Grandi told the press in Addis Ababa.
"Since April 2023, so less than a year ago, eight million people have been displaced from their homes in Sudan," he said, adding that more than 1.5 million had fled to six neighbouring countries.
The conflict between Sudan's army chief Abdel Fattah al-Burhan and his former deputy, Mohamed Hamdan Daglo, commander of the paramilitary Rapid Support Forces (RSF), erupted last April.
Diplomatic efforts to end the violence continue after numerous ceasefires have been broken.
Grandi, who was later to visit Sudan, called on donors to boost support for the influx of refugees, warning that only 40 percent of funding had been provided.
"This is not acceptable," he said. "I understand that there are more crises that are more visible. But it does not mean that this is not urgent."
"I heard stories of heartbreaking loss of family, friends, homes and livelihoods," UNHCR quoted him as saying.
As of January 21, the number of people displaced stood at 7.6 million, with children accounting for about half, according to the UN Office for the Coordination of Humanitarian Affairs (OCHA).
Over 100,000 people, nearly half of them Sudanese, have fled into Ethiopia, according to latest UN estimates.
The number of people who have gone to Chad since the war began crossed 500,000 last week, and an average of 1,500 flee into South Sudan each day, the UN statement said.
By January 21, almost 517,000 people had been recorded crossing the border from Sudan to South Sudan, OCHA said.
The war -- which has flared in the capital Khartoum -- has killed thousands, including between 10,000 and 15,000 in a single town in the western Darfur region, according to UN experts.
Sudan's army-aligned government this month spurned an invitation to a summit organised by the East African bloc IGAD and subsequently suspended its membership in the group for engaging with Daglo.
Both sides have been accused of war crimes, including the indiscriminate shelling of residential areas, torture and arbitrary detention of civilians.
