Survivors of the shipwreck are seen after their rescue on Thursday.
CNN  — 

At least 30 refugees and migrants drowned off the coast of war-torn Yemen after their boat capsized amid reports of gunfire being used by traffickers, the United Nations said Friday.

The overcrowded boat, which had more than 150 Somalis and Ethiopians on board, left from near the city of Aden on Tuesday headed across the Gulf of Aden toward Djibouti, said the UN’s International Organization for Migration, citing survivors.

“The vessel is believed to have been operated by unscrupulous smugglers who were attempting to take refugees and migrants to Djibouti, while also trying to extort more money from these refugees and migrants,” an IOM statement said.

“The boat capsized amid reports of gunfire being used against the passengers.”

About two-thirds of the passengers were Ethiopian and a third were Somali, the IOM said. It and partner organizations have been helping survivors with food, water and medical help.

Speaking at the World Economic Forum in Davos, Switzerland, on Friday, IOM Director William Lacy Swing said the organization was “deeply troubled” by the latest report from Yemen. “As we have been saying for almost five years now, the preservation of human life is our utmost priority everywhere,” he said.

Rescued migrants are pictured back on shore on Thursday.

According to a report this month by the UN refugee agency, UNHCR, there are currently more than 280,000 refugees and asylum seekers from other countries in Yemen, traditionally a transit hub for people fleeing the Horn of Africa.

Some 5,000 more arrive by sea each month – unaccompanied children among them – despite Yemen’s prolonged civil war and rapidly deteriorating humanitarian conditions, the UN agency said. While many hope simply to transit through the country, on arrival they face the threat of abduction, extortion, physical abuse and arbitrary detention, the report said.

Some later seek to flee again, putting their lives in the hands of people smugglers.

Lynn Maalouf, director of research for the Middle East at Amnesty International, said refugees and migrants were suffering alongside Yemen’s civilian population.

“This heartbreaking tragedy underscores, yet again, just how devastating Yemen’s conflict continues to be for civilians,” Maalouf said.

“Amid ongoing hostilities and crushing restrictions imposed by the Saudi Arabia-led coalition, many people who came to Yemen to flee conflict and repression elsewhere are now being forced yet again to flee in search of safety. Some are dying in the process.”

According to the United Nations, more than 5,500 civilians have been killed in Yemen since March 2015, when a coalition led by Saudi Arabia launched a military campaign against Iranian-backed Houthi rebels in the country.

Meanwhile, nearly 2 million children are suffering from acute malnutrition in Yemen, according to UNICEF, and a staggering 1 million people have been stricken by cholera.

CNN’s Spencer Feingold contributed to this report.