Vienna has also outlined plans to erect a fence at a border crossing with Italy.

With migrants crossing the Mediterranean from Africa to Italy in growing numbers, Austria has said Rome must stop them or it will have to introduce border controls at the Brenner Pass in the Alps. Building work began two weeks ago on some facilities at Brenner, but the scale of the work is not clear as yet.

The move has escalated a stand-off between the two states over how to handle the migration crisis. Italian Prime Minister Matteo Renzi said Austria's move was "shamelessly against European rules, as well as being against history, against logic and against the future".

Austria has taken an increasingly hard line on dealing with asylum-seeking migrants, especially since an anti-immigration Freedom Party candidate won Sunday's presidential election.