The UN refugee agency says 16 African migrants have died and another 49 are missing and presumed dead after trying to cross the Gulf of Aden in three boats.
The UN High Commissioner for Refugees (UNHCR) says the first smuggler's boat capsized because of an engine failure on Sunday off Yemen's coast.
It says most of the passengers on the vessel coming from Somalia managed to swim ashore but 43 are missing and presumed dead.
One person suffocated in the boat's engine room.
UNHCR said 10 people on a second boat died from asphyxiation in the engine room and another three were beaten to death by the smugglers. The boat reached Yemen on Sunday.
The agency says another two migrants drowned and six went missing when a third boat sank in deep waters yesterday. A Belgium warship managed to rescue 38 of the passengers.