GENEVA (Reuters) - About 1,500 refugees and migrants are trapped in detention centers by the Libyan conflict and the risks to their lives are growing by the hour, the head of the U.N. refugee agency said on Friday.

“These are people in the most vulnerable and dangerous of circumstances,” U.N. High Commissioner for Refugees Filippo Grandi said in a statement, calling for them to be evacuated.

“They must be urgently brought to safety. Simply put, this is a matter of life or death.”