ISTANBUL—Iraqi Kurdish forces arrived early Wednesday in Turkey en route to reinforce a Kurdish militia battling Islamic State militants in the Syrian city of Kobani, a ground intervention that will be the first by a Western-backed foreign force since the Syrian conflict began.

The semiautonomous Kurdistan Regional Government in northern Iraq sent some 160 fighters to Turkey on Tuesday, said Fuad Hussein, chief adviser to KRG President Massoud Barzani.

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