Serbia's prime minister has denounced neighboring Hungary's razor-wire border fence to stop migrants, comparing it to Nazi-era concentration camps.

Prime Minister Aleksandar Vucic spoke as he talked to migrants from the Middle East, Africa and Asia who were camping Wednesday in a Belgrade park. He said Serbia has no plans to build fences on its border even though it is being overwhelmed by the flood of migrants.

Vucic says "we won't build those wires, those barbed wires. It only takes for someone to switch the electricity through those wires and to finish the job."

Serbia, on the main transit route for migrants who want to reach Western Europe, fears when the fence is completed, it will leave thousands of people stranded inside the Balkan country.