"The number is made up of 70 percent women, 15 percent girls, 10 percent men and 400 repatriated," said the UNHCR in a tweet Saturday, the authenticity of which was confirmed Sunday by one of the agency's Central Africa representatives.
Millions of Sudanese have been trapped in their homes during heavy fighting between the forces of army general Abdel Fattah al-Burhan and his former deputy, General Mohamed Hamdan Dagalo, who heads the paramilitary Rapid Support Forces.
Central African Republic, which lies to the southwest of Sudan, is one of the poorest countries in the world.
It has itself been in the throes of civil conflict since 2013, when a Muslim-majority rebel coalition, the Seleka, ousted former president Francois Bozize.
On Thursday, the UN's humanitarian coordination agency (OCHA) announced that nearly 3,000 people had entered the country in the northeast province of Vakaga, which borders Sudan, and were living in makeshift camps.
With traffic between the two countries severely disrupted, the prices of essential products have soared, the agency said, expressing concern for the effect that would have on the 120,000 in the north of the country who needed immediate food aid.
The UN says 75,000 people fleeing the fighting have been displaced inside Sudan, while another 20,000 have fled to neighbouring Chad, to the west. Another 4,000 have fled south to South Sudan and 3,500 to Ethiopia in the south-east.