South Sudan is facing a "huge humanitarian crisis" that requires support from the international community, the United Nations' refugee chief said Sunday.

Nearly 80,000 refugees have entered the nation from neighboring Sudan, where fighting has flared in the states of Southern Kordofan and Blue Nile, U.N. High Commissioner for Refugees Antonio Guterres said. And ethnic conflicts in South Sudan have displaced thousands, he said.

"My appeal is for the international community to stand by South Sudan and to support this country that became a sovereign state just six months ago to be able to cope with the challenges," Guterres told CNN in an interview via Skype from South Sudan.

Last weekend, some 6,000 armed men from the Lou Nuer tribe marched on an area of South Sudan's Jonglei state, which is home to the rival Murle tribe, attacking the town of Pibor.