Six African migrants drowned and 11 more are presumed dead after smugglers in the Gulf of Aden forced their passengers overboard in deep water off Yemen, the U.N. refugee agency reported Tuesday.

A smuggling boat was carrying 40 Somalis and 12 Ethiopians when it approached Yemen's coast on Friday, said Ron Redmond, spokesman for the U.N. High Commissioner for Refugees. But smugglers noticed Yemeni police onshore and panicked, forcing the passengers overboard in deep water, he said.

Redmond said 35 passengers were able to make it safely to shore, while authorities have recovered six bodies. Eleven people are missing.

It was the latest incident of brutality against the mainly Somali refugees who are trying to make the treacherous voyage from the Horn of Africa to the Arabian peninsula. Hundreds die every year, with many drowning or being attacked by pirates.

Redmond said this year's death toll stands at 47.

The U.N. refugee agency says over 50,000 migrants last year crossed the Gulf of Aden, which links the Indian Ocean to the Suez Canal and the Mediterranean Sea. Nearly 10,000 more migrants have already arrived in Yemen this year.