Vienna (dpa) - The Austrian army on Monday began constructing a fence along the border with Slovenia, which was designed to control thousands of migrants, even though arrival numbers have dwindled in the past days.The fence is 2.2 metres high and will run for nearly 4 kilometres left and right of the border crossing at the town of Spielfeld, police spokesman Leo Josefus confirmed."It enables us to channel people so that they cross only at one point," he explained.Conservative Interior Minister Johanna Mikl-Leitner had proposed the barrier in late October in response to thousands of migrants crossing the border each day.Mikl-Leitner said the fence would increase safety for migrants, but she has also openly called for making Austria a less attractive destination.Since October, the number of people travelling through the Balkans and on to Austria and Germany has dropped, after countries on the Balkan route stopped allowing entry to economic migrants and built their own fences.The colder weather and Turkish efforts to stop people smuggling into Greece have added to the downward trend."Over the past days, there were zero" arrivals in Spielfeld, Josefus told dpa. Some 1,200 people arrived on Monday, he said.