At least 74 African migrants were missing after their boat capsized off Yemen, the U.N. migration agency said Monday, adding to fears that the disaster may have left more than 140 dead.

Yemen is at the crossroads of the Arabian Peninsula and the Horn of Africa. The country has long been a transit point for migrants, mostly from Ethiopia, Eritrea, Djibouti and Somalia, trying to reach the rich Gulf states to the north. The journey, known as the Eastern Route, is among the most perilous in the world.

Abdusattor Esoev, the head of the International Organization for Migration in Yemen, said on Monday that 12 people had survived but 68 bodies had been recovered since the disaster on Saturday night. At least 74 migrants were still missing, as their vessel tried to cross the sea from the Horn of Africa to Yemen.

“We know that most of the migrants on board were Ethiopian nationals,” Mr. Esoev said.

Local officials in Yemen said search-and-rescue operations were continuing, even as worries grew that many more had not survived.

“Many of the bodies have been found scattered along various parts of the coastline, raising fears that more victims remain missing at sea,” the authorities in Abyan, a southern Yemeni province, said in a statement posted on Facebook. The post included images that showed many of the dead had not been wearing life vests when their bodies washed ashore.

Mr. Esoev said overcrowding and a lack of safety equipment were likely factors. “The underlying cause of boats capsizing in the Eastern Route is due to smugglers filling boats over capacity and not providing enough life vests on board,” he said.

The disaster is the latest in a series involving undocumented African migrants attempting to reach the Gulf states by crossing Yemen, which shares a long, porous border with Saudi Arabia.

Many of these migrants are fleeing conflict, poverty and extreme weather events, some linked to climate change.

In March, at least two people were confirmed dead and 186 others were feared to have drowned after four migrant boats capsized between Yemen and Djibouti.

Yemen has been engulfed in a civil war for more than a decade, when Iran-backed Houthi militia forces ousted the internationally recognized government. The conflict has claimed hundreds of thousands of lives, caused multiple humanitarian crises, through violence, famine and disease. Millions of people in Yemen have been displaced and struggle for food.

The conflict and political instability have made it an increasingly dangerous destination for African migrants who have often been caught in the crossfire of the country’s problems. In April, at least 60 migrants were killed when U.S.-made bombs struck a detention center in the northern province of Saada, according to health officials in the Houthi-controlled government.

For years, many migrants also have been trapped in Yemen sometimes because of closed borders and limited job opportunities in the Gulf. They often face abuse and sexual exploitation, according to aid groups. Others are trafficked by smugglers who demand more money from them or their families back home in order to release them.