Thousands of migrants stranded on Greek islands should be quickly transferred to the mainland or other European countries due to cold temperatures and poor living conditions, the United Nation's refugee agency (UNHCR) said today. About 15,000 people living in the overcrowded island camps do not have enough heating or supplies to keep warm during the winter months, the UNHCR said. "Even with recent efforts to improve matters, conditions at many sites on the islands remain very poor," UNHCR spokesman Adrian Edwards said. "The need for better protection will become all the more acute this weekend when temperatures on the islands are expected to drop. We are worried."