Turkish President Tayyip Erdogan accused the United States on Monday of supporting Kurdish militants who Ankara says executed 13 kidnapped Turks in northern Iraq, adding that a U.S. statement of condemnation was a "a joke."

Turkey said on Sunday militants from the outlawed Kurdistan Workers Party (PKK) executed the 13 Turks, including military and police personnel, amid a military operation against the group. Washington said it condemned the killings if reports that the PKK was responsible were confirmed.

Erdogan told supporters of his AK Party that the U.S. statement showed it supported the PKK and the Syrian Kurdish YPG force, which Ankara considers an offshoot of the PKK.