Turkey's army said on Saturday it hit shelters and hideouts used by militants from three groups - (PKK), PYD and YPG, after militants fired on Turkish positions inside Turkey. Turkish President Tayyip Erdogan said on Saturday a military operation in Syria's Kurdish-controlled Afrin region had begun after cross-border shelling by the Turkish army. Erdogan has repeatedly said he would crush the Syrian Kurdish militia in Afrin, which he views as a security threat to Turkey. Direct military action against territory held by Kurdish militia opens a new front in Syria's civil war and sees Ankara confronting Kurds allied to the United States at a time when Turkey's relations with Washington are reaching breaking point. The U.S. State Department called on Turkey to focus on the fight against Islamic State militants and described Turkish activity in Afrin as destabilizing.