Human rights group Médecins Sans Frontières have documented hundreds of unregistered migrants in the Una Sana Canton at the Bosnia/ Croatia border.
The migrants are living in unofficial shelters, on the streets and the Vucjak camp, which the organisation describes as "completely inhumane".
There is no access to basic services, and the group are exposed to extreme weather conditions. MSF have said they "cannot rule out that people may die" with Winter approaching.
The camp was intended to be a temporary solution by local authorities to provide shelter for those left out of the official camps, but is situated in area surrounded by landmines, and where the soil is contaminated with methane.
On Wednesday, it was announced that the camp will stay open for winter and house new arrivals.
MSF doctors working in clinics in Velika Kladusa and near the Vucjak camp have begun treating skin infections such as scabies and body lice and respiratory tract infections.
MSF has called for the immediate closure of Vucjak ahead of winter, and an increase of capacity in the official camps.
One man from Pakistan, who has been staying at the camp with his 16-year-old brother said: "The situation is very hard here – I never had to sleep in a tent before. At night the cold passes through the tent, and when it rains the water gets inside the tent.
"The food is really bad, the toilets are so dirty that we cannot use them, and the water for showers is freezing cold.”
MSF's Deputy Field Coordinator Nihal Oman said the camp "is a dangerous and inhumane place" and that "no human being should live like that"
"It’s heartbreaking to see and treat these people, knowing that at the end of the day they will have to go back to a tent and sleep on the floor. It is unacceptable to hear that this camp will remain open. It should be closed now.”
Approximately 20,000 people have arrived in Bosnia this year with hopes to continue their journey north to Europe. Bosnia is being described as a "one of the toughest migration bottlenecks in Europe" as security measures become more restrictive among the Balkan borders.