Turkey says that U.S.-backed Kurdish militia in Syria are providing arms to Kurdish rebels fighting Ankara, citing as evidence a joint U.S.- and Swedish-made anti-tank rocket reportedly seized from the rebels.

Turkey considers the Kurdish People's Protection Units, or YPG, an extension of the outlawed Kurdistan Workers' Party, or PKK, and views it as a terrorist organization.

The Syrian Kurdish force, however, is a U.S. ally in the fight against the Islamic State group.

Turkish Prime Minister Binali Yildirim said Wednesday that the rocket seized during anti-PKK operations near the Syrian border showed that the YPG was transferring U.S.-provided arms to the PKK.

Pentagon spokesman Chris Sherwood said the weapons aren't meant for the PKK, and the U.S. doesn't know that any of the arms have gone to the group.