The U.N. refugee agency says a record number of people - 103,000 - crossed from the Horn of Africa to Yemen last year, fleeing violence, poverty, and the regional drought.
The number of crossings nearly doubled from 2010, and is 25,000 higher than any other year in the agency's records.
UNHCR spokesman Adrian Edwards said Friday that three-fourths of the migrants came from Ethiopia. He says many Ethiopians told the agency they left home to seek economic opportunity, and look at Yemen as a transit country to other states.
Most of the other migrants came from Somalia, which endured a year of grueling conflict and drought, leading to famine in parts of the south.
The agency expressed concern about the perilous conditions migrants face crossing the Gulf of Aden and Red Sea, and said they also face abuse and poor access to basic needs like water and shelter in Yemen.
Yemen is struggling with an ongoing political crisis, and the UNHCR says the instability and a reduced police presence are exposing the migrants to robbery, abductions, and extortion.
It says in one incident this week, three Ethiopians were killed by smugglers operating along Yemen's Red Sea coast. It says that according to initial reports, the Ethiopians were shot trying to escape from human smugglers who were trying to extort money.