About another 200,000 South Sudanese refugees are expected to arrive in Sudan this year, fleeing fighting and food insecurity in their country, the United Nations said Thursday.
South Sudan, the world's youngest nation, descended into civil war just two years after it split from the north in 2011.
Since the war erupted in late 2013, 417,000 South Sudanese refugees have already crossed into Sudan, according to the UN.
About 200,000 more refugees are expected in 2018, the United Nations Office for the Coordination of Humanitarian Office, or OCHA, said in its latest bulletin.
"Continued fighting, limited humanitarian assistance and extreme levels of food insecurity are forcing citizens of South Sudan to seek refuge, safety and access to food and basic services in neighboring countries," OCHA said.
"The government of Sudan maintains an open border policy for the refugees, ensuring unfettered access, immediate protection and safety within Sudan's borders."
Most new refugees arriving in Sudan are expected to cross into White Nile, East Darfur and South Darfur states, OCHA said.
South Sudan's leaders fought for decades for independence from the north, but an internal civil war erupted in December 2013 out of a power struggle between President Salva Kiir and his former deputy Riek Machar.
The war has caused tens of thousands of deaths, uprooted nearly four million people -- roughly a third of the population -- and triggered sporadic outbreaks of famine.