Serbia will never close its borders to migrants, Prime Minister Aleksandar Vucic told Reuters on Wednesday, but he said EU leaders must help frame a plan on how to cope with the tens of thousands pouring into the Balkan region.

About 100,000 migrants, many of them from Syria and other conflict zones in the Middle East, have entered Serbia this year on their way north to Hungary and Europe's Schengen zone of passport-free travel. Hungary is building a 3.5-meter high fence along its 175-km (110-mile) border with Serbia seeking to keep the migrants out.

"We will never erect any fences, any walls," Serbian Prime Minister Aleksandar Vucic said in an interview ahead of the Western Balkans Summit in Vienna.