Graphic pictures have shown the aftermath of tear gas and water cannon used on people at the Hungarian border on Wednesday.
In one particularly shocking set of images, a man with blood streaming down his face is shown cradling a terrified child, while riot police stand with shields raised and tear gas swirls around.
Other pictures showed people trying to wash tear gas from their eyes and reacting to police.
On Thursday, Hungary's ambassador to the United Kingdom defended his country's treatment of refugees after the UN Secretary General said he was "shocked" at its behaviour.
Peter Szabadhegy told BBC Radio 4's Today programme this morning that the criticism of Hungary was "misplaced".
"Hungary is facing a huge migration crisis, just to put it into perspective, just a year to date there have been 200,000 migrants who have crossed Hungary's border. That is exceeding the size of the second largest city in Hungary," he said.
And he said it Hungary had a right to prosecute refugees who "vandalise fences and attack police".
A man cradles a child after police fire tear gas at people near the Hungarian border
The incident took place after refugees broke through a razor wire fence at the country’s border with Serbia.
Some frustrated migrants threw plastic water bottles and rocks at helmeted riot police and chanted demands that the border be re-opened.
The clashes took place at a small border crossing in the Serbian village of Horgos, a short distance from the main border crossing into Hungary.
Before the tensions escalated, some women pushed to the front of the crowd and held small babies and children above their heads as they faced police in an obvious appeal for mercy, but no one made it through.
Serbian authorities sent ambulances to the site but it wasn't immediately clear how many people were injured, according to AP.
Hungarian authorities said on Wednesday that they had arrested a total of 519 migrants who tried to cross the border since tough new laws went into effect on Tuesday that make it a crime to cross from Serbia anywhere other than at legal checkpoints.
Many of those attempting to cross the borders are refugees from war-torn countries such as Syria, Iraq and Afghanistan.
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