Hundreds of refugees have pushed through police lines in the eastern Croatian town of Tovarnik.
More than 2,000 men, women and children were stuck at the local train station for hours in blazing heat and sun, waiting to board trains and buses for transport to refugee centres.
When buses arrived, groups charged toward them, overwhelming the Croatian police who unsuccessfully tried to contain the crowd.
After the situation calmed, groups of refugees moved off on foot, with police unable to stop them.
Croatian police say 7,300 refugees have entered the country after the flow of people fleeing war and poverty moved in its direction after Hungary sealed its border with Serbia.
Police say refugees have been coming into Croatia through four entry points.
Upon entry, refugees are taken to refugee centres where they are registered and can apply for asylum. But, most have said they do not want to stay in Croatia and are eager to move on toward Western Europe.
Hungary has used tear gas, water cannons and pepper spray to keep the refugees away from its territory.