RAQA/ERBIL, Jan. 24 -- Europeans were among 150 Islamic State (IS) detainees this week transferred by the US military from Kurdish custody in Syria to Iraq, where Prime Minister Mohammed Shia al-Sudani urged European countries to repatriate their nationals.

The detainees were part of an estimated 7,000 IS members slated for transfer as Kurdish-led forces relinquish territory to the advancing Syrian army. The US said its alliance with the Kurds had largely expired following Syria's renewed territorial offensives, prompting the Syrian Democratic Forces (SDF) to withdraw from areas in the north and east.

According to Iraqi security officials, the 150 transferred detainees included "all leaders of IS, and some of the most notorious criminal...