The U.N. says at least 30 African migrants and refugees have drowned after their boat capsized off the coast of Yemen earlier this week.

Friday's statement by the U.N. Migration Agency says the overcrowded boat, carrying some 152 Somalis and Ethiopians, was heading from the al-Buraiqa coast near the Yemeni city of Aden toward Djibouti.

The IOM says the vessel is believed to have been operated by "unscrupulous smugglers" who tried "to extort more money" from the migrants. Survivors reported gunfire as the boat capsized.

Yemen has been embroiled in a civil war pitting a Saudi-led coalition backing an internationally recognized government against Iran-backed Shiite rebels since March 2015.

The IOM says Yemen's conflict has subjected refugees and migrants to risk of human rights violations, including arbitrary arrest and trafficking.