All traffic in the border area, between 300 and 700 metres from the border with Serbia, is banned until further notice, the Ministry of the Interior said.
Interior Minister Ranko Ostojic said that he expected that the train station in the border town of Tovarnik would be vacated during the night as trains were taking refugees to Beli Manastir where accommodation had been prepared for 2,000 people.
Refugees might try to continue their journey from Croatia to Slovenia and on to Western Europe as their desired destination. They were gathering in small groups at Zagreb's central railway station on Thursday in efforts to board trains for Slovenia, the HTV public television network reported.
Zagreb Mayor Milan Bandic said earlier that up to 1,200 refugees could be put up at the Trade Fair Centre where several thousand bottles of water, dry rations, mattresses and toilets had been prepared.
Slovenian police said on Thursday they had taken off about 150 migrants from a train in Dobova and would send them back to Croatia as soon as they received a confirmation from Croatian security services. They said that a group of about 20 migrants had also attempted to cross the border at Bregana but had been stopped by the Croatian border police, adding that the situation was now calm there.
French news agency AFP quoted Slovenian police as saying that a train with 150 migrants who had been stopped at the border with Croatia was on its way to the centre for foreigners in the western town of Postojna. This was the first group of migrants to enter Slovenia after Hungary closed its border with Serbia and refugees started heading to Croatia in their efforts to reach Western Europe.
During a regular check of a train on the border, we found that 150 of 300 passengers did not meet the requirements for entry into Slovenia, a spokesman for the Slovenian border police was quoted by AFP as telling reporters in Dobova. The authorities are preparing their return to Zagreb as soon as possible, he added.
Slovenian police would not say why they had eventually allowed the migrants into Slovenia.
The Slovenian rail company announced on Thursday evening that it had cancelled indefinitely all international trains coming from Croatia via Dobova because they might be used by migrants.
Slovenian Prime Minister Miro Cerar said on Thursday that statements by the Croatian minister of the interior about corridors for refugees were "unfair and dangerous" and that Slovenia had never discussed such a possibility with Croatia. "There has never been any such agreement and there can't be. Slovenia is enforcing the Schengen regime on the border with Croatia. We cannot allow people who do not meet the criteria for entry into the EU across the Schengen border and Croatia is well aware of that," Cerar said.
Meanwhile, Serbian Labour and Welfare Minister Aleksandar Vulin called on Croatia not to close the border and international roads because otherwise Serbia would seek protection before international courts. "We wish to warn Croatia and any other countries that closing the international roads is out of the question and that we will seek protection of our economic and all other interests before international courts," Vulin told Tanjug news agency in Horgos, on the border with Hungary, following Croatia's announcement that it might close its border due to the growing influx of refugees.
"We won't pay the price of other people's incompetence. If Croatia is unable to cope with 6,000 migrants, Serbia will send it the necessary aid and people who have coped in recent months with 140,000 peaceful and civilised people who didn't cause a single incident," Vulin said, adding that he regretted to see that "Croatia's humaneness and solidarity lasted only two days."
Hungary has extended a crisis situation to territories neighbouring Croatia from counties on its Serbian border due to the streams of refugees and migrants, Hungarian Foreign Minister Peter Szijjarto told a news conference on Thursday, according to Reuters news agency.
"What is Croatia doing? Instead of providing the proper care to immigrants and registering them, it sends them on towards Hungary and Slovenia," he said, adding that Croatia's system to provide care to migrants collapsed in one day.
The ministry had summoned Croatia's ambassador to complain, Szijjarto said, adding that Croatia proved now that it was not prepared to join the European Union's visa free Schengen zone for at least several more years.