Police have removed hundreds of migrants from a camp at Greece's border with Macedonia following a protest that halted freight rail services to other Balkan countries.

Authorities said the mostly Afghan migrants were being put on buses bound for Athens, in the south of the country, after the police operation started early Tuesday. Journalists were not allowed to approach the area.

Macedonia at the weekend began stopping Afghan migrants at the border, and slowing the rate at which asylum seekers from Syria and Iraq were allowed to cross the border — leaving thousands stranded in Greece, where an average of 4,000 migrants and refugees each day.

Greek has strongly criticized Austria's decision last week to cap the daily number of asylum applications and migrants crossing the country.