More than four thousand migrants have crossed into Hungary from Croatia, by train or bus.
They moved on Friday under the watch of Hungarian security forces, under orders to keep them out.
It was a snapshot of the confusion and contradiction engulfing a divided Europe.
The development came hours after Croatia said it could not take any more migrants, with more than 17-thousand flowing into the country since Wednesday morning.
The migrants were taken to two registration points, close to the Austrian border, according to police.
Hungary has denied organising the move with Croatia, while Austria has denied coordinating it with Budapest.
Confusion is being felt by the migrants. One man said he thought he was being taken to Slovenia.
People have been streaming into Croatia after Hungary introduced tough anti-migrant legislation and put up a razor wire fence along its border with Serbia.
Another fence has been going up along Hungary’s border with Croatia.
Euronews reporter Attila Magyar said: “During Friday, the situation changed a few times, but the refugees and migrants were not told about what was happening.
“There was some information circulating that they would be taken to Slovenia, to Hungary, to Austria. One thing is for certain, Croatia has struggled to cope with the crisis.”