The escalating migrant crisis is causing bitterness between two European countries as Hungary accused Croatia on Friday of committing “a major violation of international law” by trying to send 1,000 migrants in trains across its border.

Sky News reports Budapest called the unannounced transport a “major, major incident,” and alleged that the dozens of police officers accompanying the migrants had to be disarmed and sent back to Croatia.

Zoltan Kovacs, a Hungarian government spokesman, said the incident showed “the Croatian system for handling migrants and refugees has collapsed basically in one day. What is more, we see intentional participation in human smuggling, taking these immigrants to the Hungarian border.”

The refugees who were on board the train to the town of Magyarboly are being transferred to a reception camp and the train driver has been arrested, according to Sky News.

Hungary has already built barbed wire fences around parts of its border with Serbia and Croatia. Sky News reports the country has helicopters searching the countryside and armed soldiers stationed in armored vehicles on the lookout.

Croatian Foreign Minister Vesna Pusic claims the two countries had agreed “to provide a corridor” to Western Europe, where most of the refugees coming from the Middle East are aiming to go. However, Kovacs told Sky News that was not true.

"These people were coming toward the border without prior consultation, without respecting official channels," Kovacs said.

Austria also said that if a corridor was being discussed, no one had told its interior ministry.

More than 4,000 migrants were sent from Croatia to Hungary on Friday after officials said it didn’t have the space for the 17,000 who arrived in Croatia on Wednesday. Busloads of migrants were being taken to registration camps to the Austrian border and others were being brought toward Slovakia, according to Sky News.

Croatia on Friday closed all its border crossings with Serbia  in an effort to halt the flow of refugees seeking a way into Western, Central and Northern Europe. None of the Balkan countries are willing or prepared to handle the crisis and have been trying to close off their borders, pushing the problem onto their neighbors.

Kovacs called Croatia’s refusal to accept more refugees “totally unacceptable.” He said Hungary has been dealing with the migrant crisis for nine consecutive months, whereas Croatia’s “supply system collapsed in a single day”

Meanwhile, Slovenia’s government said Friday it will accept asylum seekers, but will send back anyone deemed to be an illegal immigrant.

An interior ministry official in Slovenia said Friday that “at the moment” the country has no basis for creating a corridor for migrants to pass through, despite the hundreds headed their way. Reuters reported.

"We estimate that about 1,000 persons will arrive within the next 24 hours," Slovanian interior ministry state secretary Bostjan Sefic told a news conference.

Slovenia claims Croatia is breaking the rules of the European Union and the Schengen zone of border-free travel. Sefic said the police were preparing additional units ahead of the influx of migrants from Croatia.

"The actions of Croatia are not in line with EU and Schengensystems as they decided they are no longer registering migrants," Sefic said. 

The U.N. refugee agency warned the crisis was being worsened by contradictory national policies.

"The crisis is growing and being pushed from one country to another," said Adrian Edwards of UNHCR. "You aren't going to solve these problems by closing borders."

The human misery was evident in Croatian towns like Beli Manastir, near the border with Hungary. Migrants slept on streets, on train tracks and at a local gas station. People scrambled to board local buses without knowing where they were going.

Hundreds of others were stranded Friday on a large Danube River bridge in the Serbian town of Bezdan after Croatian authorities closed all but one border crossing. A large truck lifted barriers onto the bridge. The group, which included many women and children, stood in a no-man's land in the middle in the scorching heat for hours with little water or food.

Hundreds of people also camped out overnight Saturday in Obrezje, Slovenia, a town just across from the border with Croatia. Authorities only allowed limited numbers of families with woman and children to continue on. Many migrants put up tents while others tried their best to keep warm as the temperatures decreased overnight.

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The Associated Press contributed to this report.