Thousands of migrants have been stranded at borders in the Balkans, in cold and wet conditions, as their options for travellingnorth shrink.
Several hundred, including young children and babies, spent the night in the open at Croatia's border with Slovenia.
The UN refugee agency (UNHCR) also complained of a lack of basic supplies at the Serbia-Croatia border.
The western Balkan route has been squeezed by government restrictions.
Hundreds of thousands of migrants, many from Syria, Africa and Afghanistan, have been making their way from Turkey to the Balkans in recent months, in a bid to reach Germany, Sweden and other EU states.
Slovenia decided at the weekend to restrict the numbers crossing its territory to 2,500 a day, in response to what it said was Austria's new policy of cutting the numbers entering.
However a spokesman for the Austrian interior ministry, Karl Heinz Grundboeck, told the BBC that there were no specific limits on the number of people allowed in each day and that migrants were continuing to arrive.
On the Croatia-Slovenia border, 500 people spent the night in the open at Trnovec.
A further 1,800-2,000 slept on a train held on the Croatian side of the border. Officials told them they could stay temporarily in Croatia or try to make their own way into Slovenia.