ANKARA (Reuters) - Prime Minister Binali Yildirim said on Tuesday Ankara will retaliate immediately if the operation by U.S.-backed forces to capture Raqqa, Islamic State’s de facto capital in Syria, presents a threat to Turkey.

Speaking to deputies from the ruling AK Party after the Syrian Democratic Forces (SDF) said they had launched their battle for Raqqa, Yildirim said Turkey was taking the necessary measures on the issue.

Turkey views the Kurdish YPG militia within the SDF as a terrorist group aligned with militants who have fought an insurgency in southeast Turkey since 1984.