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The head of the United Nations refugee agency is urging countries, particularly in Europe, to open up more to Syrians fleeing their country's civil war.

Antonio Guterres says a refugee crisis across the Middle East is a global security threat. He urged more legal avenues for Syrian refugees to resettle in Europe, and avoid risking their lives with smugglers.

The U.N. estimates that nearly 2.7 million Syrians have fled abroad, mostly to neighboring countries, and another 6.5 million are internally displaced.

Guterres spoke in the United Arab Emirates at a Wednesday conference on child refugees. He said that on average, a child is forced to flee his or her country in the Arab world every minute. In attendance was Queen Rania of Jordan, which hosts some 600,000 Syrian refugees.