(Adds details, background) GENEVA, Dec 29 (Reuters) - More than 150 people were presumed dead on Friday after two boats of would-be migrants fleeing Somalia capsized off the coast of Yemen, the United Nations refugee agency said. "The confirmed death toll is now 34. The 123 still missing are presumed dead," said William Spindler, spokesman for the U.N. High Commisioner for Refugees (UNHCR). The UNHCR had said on Thursday at least 17 people were killed and 140 missing after the incident, which took place late on Wednesday after Yemeni security forces opened fire on smugglers trying to bring more than 500 people into the country, across the Gulf of Aden. Two boats had offloaded their passengers and were then fired upon by Yemeni security forces. A third boat capsized after being unbalanced by agitated passengers, and the fourth was pursued by Yemeni coastguard boats and a helicopter, and capsized in heavy seas some 300 metres from the beach. Spindler said the majority of the 357 survivors were Somalis, and 75 were Ethiopians. About half of the Somalian survivors said they were fleeing fighting between Ethiopian-backed Somali government forces and rival Islamists, Spindler said. UNHCR has asked neighbouring countries to be prepared to accept those fleeing. Somali Prime Minister Ali Mohamad Gedi swept into Mogadishu in an armed convoy on Friday after the Islamists fled the city they had ruled for six months. More than 25,800 people have been recorded arriving in Yemen from Somalia this year, according to UNHCR. The boats from Somalia usually land along a remote stretch of tribal-ruled coastline.
