UNITED NATIONS, June 15 (Xinhua) -- The UN Refugee Agency ( UNHCR) reported that some 14,000 South Sudanese, mainly women and children, fled into Sudan over the weekend, describing the situation as an emergency within an emergency, UN spokesman Stephane Dujarric told reporters here Monday.

"UNHCR has registered close to 160,000 refugees in Sudan since fighting broke out in South Sudan in December 2013," Dujarric said at a daily news briefing here. "A key priority for the humanitarian community is to prepare for the upcoming rainy season, which is due to start in the coming weeks and will further complicate operations."

Rapid scaling up of water, sanitation and hygiene interventions is critical as rains will also heighten the risk of water-borne diseases such as dysentery and cholera, he said, adding that so far only 10 percent of the 152 million U.S. dollars requested to assist South Sudanese refugees in Sudan has been contributed.

Meanwhile, the humanitarian situation in South Sudan has deteriorated significantly over the past two months with the intensification of military operations in Upper Nile and Unity States. It is estimated that by July some 4.6 million people could be severely food insecure -- the highest number since the beginning of the crisis, according to the spokesman.

The security situation in South Sudan has deteriorated steadily over the past year since political in-fighting between President Salva Kiir and his former vice president, Riek Machar, and their respective factions erupted in December 2013.

The hostilities subsequently turned into a full-fledged conflict that has caused more than 110,000 civilians to seek safety on bases belonging to the UN Mission in country (UNMISS).