The U.N. refugee agency says 17 people are confirmed dead and some 140 missing after the smugglers' boats they were traveling in from Somalia across the Gulf of Aden capsized off the Yemen coast. The UNHCR says this incident occurred late Wednesday. It involved four boats smuggling 515 Somalis and Ethiopians. Lisa Schlein reports for VOA from UNHCR headquarters in Geneva.

The U.N. refugee agency calls this one of the worst incidents seen to date. Yemeni authorities say a gun battle ensued between their security forces and the smugglers after they off-loaded their human cargo. They say two of the ships tried to escape back to sea. One capsized and the other was forced back to shore.

The Yemeni authorities say they have captured all 17 smugglers and their four boats, and that a search operation is still underway for survivors.

UNHCR Spokesman, Ron Redmond, tells VOA the prospect of finding anyone alive is slim.

"UNHCR is extremely concerned about this incident for a number of reasons including the fact that with the violence that is taking place in Somalia now we may be seeing more people taking to these smugglers' boats to cross the Gulf of Aden in the coming weeks," he said. "And, this is a very dangerous thing to do because these smugglers are very brutal people and have been known to beat people to death aboard those boats. They have thrown people overboard to the sharks."

More than 25,800 people have arrived in Yemen from Somalia this year. At least 330 people have died making the dangerous journey and nearly 300 are missing, including 141 from this current incident.

U.N. High Commissioner for Refugees, Antonio Guterres, says a concerted international effort is urgently needed to address the root causes of the human trade. He says action must be taken to educate would-be migrants and to crack down on the smugglers and traffickers based in Somalia.

Redmond says many of the 357 survivors say they fled from troubled areas in Central and Southern Somalia. And, many say they fled the current conflict between the Somali transition government and the Islamic Courts Union.

"It is not clear if the conflict they are referring to is what has been transpiring over the past week or so or if it is something earlier," he said. "But, they say that they are fleeing conflict, violence, persecution. And, in the past, we have also had people saying they were in search of better economic opportunities. So, it is a mix of reasons why these people are fleeing."

Redmond says the 357 survivors have been taken to a UNHCR reception center to recover from their ordeal. He says they are receiving food and medical assistance.