A group of migrants trying to enter Macedonia threw stones at cops on Saturday as the small Balkan country became the latest to build a border fence aimed at controlling the flow of desperate refugees.

Eighteen cops were hurt in the protests at the Gevgelija crossing point between Greece and non-EU member Macedonia as troops began to erect an 8-foot fence, AFP reported.

Syrians, Afghans and Iraqis are flowing largely unimpeded across the Balkans after arriving in Greece from Turkey, but other nationalities are being turned back.