Turkey's President announced that a Turkish military helicopter was downed in northern Syria on Saturday during Ankara's offensive on Syrian Kurdish militia there. <br/><br/>Speaking in Istanbul, President Recep Tayyip Erdogan did not mention by name the Syrian Kurdish People's Protection Units but said that those responsible will pay for it.<br/> <br/>A spokesman for the Kurdish militia, Mustafa Bali, said his fighters downed the chopper in Raju, northwest Afrin. <br/><br/>But the Turkish Prime Minister said the cause of the helicopter's crash is not yet clear and investigations are going on.<br/><br/>