At least 55 people are believed to have drowned after a boat capsized off the coast of Somalia, the UN refugee agency says.The UNHCR said the overcrowded boat ran into trouble soon after it left the port of Bosasso in north-east Somalia.The boat - believed to be carrying Somalis and Ethiopians - had been on its way to Yemen.The UN said it is the biggest loss of life in the Gulf of Aden since February 2011 when 57 Somali migrants drowned."Twenty-three bodies have been recovered. The 32 remaining passengers are presumed to have drowned," the UNHCR said.It added that at least five people had survived the accident, which happened on Tuesday."Without doubt, the Gulf of Aden is now the deadliest route for people fleeing conflict, violence and human rights abuses in the Horn of Africa," said UNHCR Representative for Somalia, Bruno Geddo.Tens of thousands of people from the Horn of Africa cross the Gulf every year.The agency said that those making the perilous journey often used unseaworthy and overcrowded boats or fell prey to unscrupulous smugglers.It said that 95 people had drowned or gone missing in the waters between Somalia and Yemen so far this year.