Greece's interior minister has compared conditions at a crowded refugee tent city on the country's border with Macedonia to a Nazi concentration camp, blaming the suffering on some European countries' closed border policies.

Panagiotis Kouroumplis told reporters he "doesn't hesitate to say" that the Idomeni camp is a modern version of the Dachau camp operated by the Nazis in Germany.

During a visit to Idomeni Friday, Kouroumplis said the situation was a result of the "logic of closed borders" by countries that refused to accept refugees.

More than 46,000 people are trapped in Greece, after Austria and a series of Balkan countries stopped letting through refugees who reach Greece from Turkey and want to go to Europe's prosperous heartland. Greece wants refugees to move from Idomeni to organized shelters.