Tensions are rising in Bosnia-Herzegovina as migrants demand to be let into the European Union, a charity has warned.

With winter approaching there an estimated 5,000 people sheltering in abandoned buildings and other makeshift camps near the border with Croatia.

The migrants are refusing to return home and some complain of heavy-handed tactics by Croatian police.

”The situation for people stuck in Bosnia is becoming very tense, with hundreds living in awful conditions in Bihac and Velika Kladusa,” wrote Doctors Without Borders on Twitter.

“As temperatures drop the situation becomes every day more difficult and tensions are rising.

“For the third consecutive day, 150 migrants are camping on a road between Bosnia and Croatia demanding the opening of the border.

“Our teams have already provided medical care to people injured in clashes with police few days ago and we are closely following the situation.”

Some of the migrants are being exploited by people smugglers, according to the border agency Frontex.

It has released footage — which you can view in the video player, above — of a person waiting near a van in Croatia at the end of September.

The agency says the vehicle was kept under surveillance and a few minutes later a group of 20 people were seen running out of nearby woods and climbing in.

Throughout the operation, the Croatian police on the ground were kept informed.

When the authorities stopped the van it was found to be dangerously overcrowded and two people smugglers were arrested.