ANKARA, Turkey—The U.N. chief for refugees says the number of refugees from Syria could increase by "two or three times" the present level by the end of the year if the country's conflict doesn't end.

U.N. High Commissioner for Refugees Antonio Guterres says the international community should work toward ending the conflict and says there is a "risk of an explosion" throughout the already volatile Middle East region if it continues much longer.

Guterres was speaking in Ankara on Sunday, days after the number of U.N.-registered refugees in neighboring countries topped 1 million.

Guterres also renewed a call for nations to help support Turkey, Lebanon, Jordan and other countries shelter the refugees.