Istanbul, Oct 21 (IANS): Turkey's Prime Minister on Friday said the obvious links between the US-backed Kurdish People's Protection Units (YPG) and the founder of the Kurdistan Workers' Party (PKK), is the cause of great damage to his country's relationship with Washington.

Binali Yildirim was referring to a photo showing fighters from the YPG posing in the Syrian city of Raqqa with a huge banner emblazoned with the portrait of PKK founder Abdullah Ocalan, Efe reported.

Yildirim lamented the US' stance, adding that this position caused great damage to the relationship between Washington and Ankara.

Ocalan has been held since 1999 in a prison on the Turkish island of Imrali, where he is serving a life sentence, and his group is listed as a terrorist organization by Turkey, the US and the European Union.

Yildirim said the photo was a proof of the result of what happens when the US tries to cooperate with one "terrorist" organization while simultaneously trying to eliminate another.

In the fight against the IS in Syria, the YPG is the largest faction of the Kurdish-led the Syrian Democratic Forces (SDF), backed by the US-led international coalition.

Asked on Thursday about the photo and YPG links to Ocalan, Pentagon spokeswoman Dana White responded to the Turkish news agency Anadolu by saying that the US would continue working with the SDF against the IS.

A few hours later, Turkish President Recep Tayyip Erdogan also referred to the photo during a press conference broadcast live on television, asking the US to explain why the image of a "terrorist leader" was on a banner in Raqqa.

Erdogan also recalled photos of Ocalan being carried by PKK sympathizers in Paris and by Kurdish protesters in Germany, accusing the EU countries of not really opposing terrorism, as their police protected these demonstrations.