Croatia has closed seven of its eight road border crossings with Serbia following a huge influx of migrants, the BBC reports.
Officials said they had no choice after more than 11,000 people entered the country since Hungary fenced off its border with Serbia earlier this week.
Huge numbers of people heading north from the Mediterranean have created a political crisis in the European Union.
Croatian officials said roads leading to the border crossings had also been shut.
The crossing on the main road linking Belgrade and Zagreb – at Bajakovo – appeared to be the only one left open.