"Around 170,000 Yemenis, refugees and third country nationals have fled to Djibouti, Ethiopia, Somalia, Sudan and some Gulf countries," the UN refugee agency (UNHCR) and International Organization for Migration (IOM) said in a statement, after aid meetings in the Kenyan capital.
The UN said it needed over USD 94 million (86 million euros) to support those fleeing the war in 2016.
Thousands have been killed and the impoverished nation plunged into profound humanitarian crisis since March, amid battles between pro-government forces supported by Saudi-led air strikes and Iran-backed rebels.
Inside Yemen, an estimated 80 per cent of people need aid, including 2.3 million forced from their homes, the UN said.
"The suffering that this conflict is inflicting on people is heart-breaking," Bourgeois said.