It says altogether, half a million Yemenis have been displaced by conflicts.
The office of the U.N.'s High Commissioner on Refugees says in the past two weeks, 1,800 people have fled their homes in the south.
Earlier, 150,000 people were forced out of their homes in the south during a year of political turmoil that has emboldened Al Qaeda.
UNHCR says that north of the capital Sanaa, tribal clashes have displaced some 52,000 people over the past three months.
The UNHCR statement Friday said 314,000 Yemenis have been displaced in the north because of a conflict involving Shiite Houthi rebels.