The sudden arrival of such a large and heavily armed Turkish contingent in a camp near the frontline in northern Iraq has added yet another controversial deployment to a war against Islamic State fighters that has drawn in most of the world's major powers.

Ankara says the troops are there as part of an international mission to train and equip Iraqi forces to fight against Islamic State.

The Iraqi government says it never invited such a force, and will take its case to the United Nations if they are not pulled out.

Washington, which is leading an international coalition against Islamic State that includes Turkey, Arab states and European powers like Britain and France, has told Ankara and Baghdad to resolve the standoff, and says it does not support deployments in Iraq without Baghdad's consent.

Political analysts saw last week's deployment in northern Iraq by Turkey, which has the second biggest army in NATO, as a bid to assert its influence in the face of increased Russian and Iranian involvement in Syria and Iraq.

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