Sudan is facing an "emergency-like situation" with nearly 1,500 South Sudanese crossing into the country each day to flee famine and war, a top Sudanese official said Thursday.

South Sudan, formed after splitting from the north in 2011, has declared a famine in parts of the country where 100,000 people are said to be facing starvation.

Each day, 1,500 South Sudanese -- mostly women and children -- are crossing into Sudan, mainly in states like East Darfur, South Darfur and White Nile, Khartoum's commissioner for refugees Hamad Elgizouli told reporters.

"We are in an emergency-like situation... and until now we have not received any donations except to meet some existential needs," he said.

"There is a flood of South Sudanese since South Sudan declared a famine three months ago."

In late March, Sudan opened a "humanitarian corridor" for delivering food aid to thousands of South Sudanese suffering from famine in Unity State and Bahr El Ghazal.

Sudanese and UN officials expect the influx of South Sudanese refugees to carry on throughout this year.

"We expect about 180,000 South Sudanese to arrive in Sudan by the end of the year," said Noriko Yoshida, the Sudan representative of UN refugee agency UNHCR.

At the start of this year, the UNHCR had expected about 60,000 South Sudanese to arrive in Sudan in the whole of 2017, but that figure was already surpassed by the end of March.

"The number is only increasing day by day... The increase in numbers show that the situation in South Sudan is bad," Yoshida said.

Aid groups have denounced a "man-made" famine caused by bloodshed in South Sudan where civil war has forced people to flee, disrupted agriculture, sent prices soaring and cut off aid agencies from some of the worst-hit areas.

South Sudan has been engulfed by war since 2013 after President Salva Kiir accused his rival and former deputy Riek Machar of plotting a coup.

More than 365,000 South Sudanese refugees, most of them women and children, have already arrived in Sudan since December 2013.