Waves of refugees seeking to enter the European Union from the south-east have been shunted from one border to another as governments disagree over the crisis.
Croatia reversed its open-door policy after 17,000 arrivals since Wednesday. It was now sending thousands of refugees or migrants north, angering Slovenia and Hungary.
Hungary says that's in breach of EU law but Croatia says it simply can't cope with the influx.
Latest reports said a train that brought migrants from Croatia ha been seized and the driver arrested, while 40 Croatian police have been disarmed.
Hungary, which is putting a fence on its border with Croatia, was reportedly sending new arrivals on to Austria.
Two EU crisis meetings will take place next week.
Many of the refugees or migrants are fleeing conflicts in Syria, Iraq and Afghanistan.
Thousands began entering Croatia from Serbia this week after Hungary closed its Serbian border, and cut off the previous route north.
Croatia had initially said the migrants would be welcome, but on Friday it said it was overwhelmed and would not become a "migrant hotspot".\
Interior Minister Ranko Ostojic said that more than 17,000 migrants had arrived since Wednesday morning and that 3000 had now crossed into Hungary.
Hungary reversed its stance from earlier in the week and let the new arrivals in. The country was now taking the refugees to two registration centres, close to the border with Austria.
Austria said it had no co-ordination with Hungary to take the refugees. It reserved the right to deny entry to refugees or migrants who did not request asylum because they wanted to continue travelling north to Germany or elsewhere.
Separately, hundreds of refugees set off for Slovenia, to the west.
Earlier, Hungary announced it was building a new fence along part of its border with Croatia.
It was Hungary's completion of a razor-wire fence along its border with Serbia earlier this week that forced Serbia to move refugees towards Croatia.
Hungary's new laws made attempts to cross its frontier illegal, and Foreign Minister Peter Szijjarto on Friday accused Croatia of encouraging "masses of people to commit a criminal offence".
Croatian officials said earlier that every border crossing with Serbia except the main road linking Belgrade and Zagreb - at Bajakovo - had been closed.
Slovenian interior ministry state secretary Bostjan Sefic accused Croatia of breaking the rules of both the EU and the Schengen free movement agreement by deciding to no longer register migrants.
It has closed its rail service to Croatia.
However, Slovenian Prime Minister Miro Cerar later said that if the pressure of arrivals became too great, it might seek to form corridors allowing migrants safe passage.
The crisis has challenged the Schengen regime, with Germany, Austria and Slovakia all reimposing checks on parts of their borders.
EU regulations dictate refugees must register and claim asylum in the first member state they reach.
But many migrants and refugees wish to continue on to Germany and Austria.
Pope helps refugee family
Meanwhile, aides to Pope Francis said he was putting up a Syrian refugee family from Damascus in a Vatican apartment.
The family - a father, a mother and their two children - were Melkite Greek Catholics with close ties to the Catholic Church.