Austria's chancellor has convened a meeting of his German, Greek and west Balkans counterparts on strategies to deal with Europe's migrant crisis.

The European leaders met Saturday at Chancellor Christian Kern's invitation to discuss how to better fortify the European Union's outer borders against illegal migration and trafficking.

Ahead of the meeting, EU Council President Donald Tusk told reporters that "since the first day of the migration crisis I have had no doubt that the main key to its resolution is restoring effective control of the EU's external borders."

The migration summit will also focus on how to keep closed the so-called Balkans route that was used last year by hundreds of thousands of people from Syria, Iraq, Afghanistan and other crisis-torn countries to reach northern Europe.