Refugee and migrant children who have made it into Hungary and Croatia are being illegally forced back across the border into Serbia, a charity has said.
Save the Children said an estimated 30 child refugees a day are expelled, often violently, from the EU countries after crossing the border from Serbia.
A deal struck last year between the EU and Turkey was intended to stem the flow of refugees arriving in Europe by boat.
But it has instead meant refugees are taking the often more deadly land route through the Balkans with Serbia, which is not an EU country but borders Hungary, Bulgaria and Romania, becoming a transit point for migrants and refugees as a result.
Often they arrive at shelters in Serbia with dog bites and having been beaten by border guards, the charity said.
In some cases their clothes and shoes have been stolen.
A 12 year old from Afghanistan told Save the Children: "During the trip I had many problems especially in the woods.
"The Bulgarian police beat us, took our money, asked us why we came to Europe. We also had problems with the mafia."
Jelena Besedic, Save the Children's advocacy manager in Serbia said: "In truth the refugee crisis has not abated. It's simply a more dangerous route, especially for children.
"The EU-Turkey deal has given smugglers a firmer grip on a hugely profitable business, incorporating increasingly dangerous tactics to circumvent authorities.
"We are seeing injuries such as dog bites and people wounded by brutal treatment as they are pushed back."