Migrants wait to cross the border from Slovenia into Spielfeld in Austria, February 16, 2016. REUTERS/Leonhard Foeger

VIENNA (Reuters) - Austria will cap the number of migrants it lets in at 3,200 a day from Friday, Austrian Interior Minister Johanna Mikl-Leitner said, calling on other countries to tighten restrictions.

Numbers coming into Austria along the main route from Slovenia have fluctuated widely over the past year, from as many as 14,000 a day to the latest figures that suggest around 1,000 are currently braving the winter cold every 24 hours.

“It’s important that every country on the Balkan route acts more restrictively,” Mikl-Leitner said in an emailed statement on Wednesday.

“A backlog on the Slovenian side... cannot be ruled out,” she added.

Austria said last month it would only consider 37,500 asylum requests this year, compared with the 90,000 it received last year.

Around 90 percent of the migrants, many of them fleeing conflict in the Middle East, keep heading north after entering Austria, trying to reach Germany and other destinations, authorities say.