UNITED NATIONS - The UN Office of the UN High Commissioner for Refugees (UNHCR) on Monday sounded alarm on the sharp increase of South Sudanese fleeing to Sudan since the start of 2017, UN spokesman Stephane Dujarric told reporters here.

UNHCR says "it has seen a significant increase in South Sudanese refugees fleeing to Sudan since January," Dujarric said at a daily news briefing here.

Initial expectations were that 60,000 refugees may arrive through 2017, but in the first two months of the year alone, more than 31,000 refugees have arrived.

Initial estimates show that more than 80 percent of the new arrivals are women and children, including unaccompanied and separated children.

"They are in need of immediate life-saving assistance, which UNHCR and its sister agencies are trying to address," Dujarric said.

Sudan is one of South Sudan's neighboring countries to host a massive influx of South Sudanese refugees. More than 1.5 million South Sudanese refugees have fled to neighboring countries in the region, around half of which are located in Uganda.

South Sudan has been shattered by civil war that broke out in December 2013 after President Salva Kiir accused his former deputy Riek Machar of plotting a coup. Machar denied the accusation but then mobilized a rebel force.

A peace deal signed in August 2015 led to the formation of a transitional unity government in April, but was again devastated by fresh violence in July 2016.

Tens of thousands of South Sudanese have been killed, with more than 2 million displaced and another 4.6 million left severely food insecure, since December 2013.