By Tania Steere: ITV News
Refugees stranded in the freezing cold in Serbia are being treated for frostbite and are at risk of hypothermia, medical charity MSF is warning.
More than 7,500 people are stranded in Serbia living in overcrowded camps and abandoned buildings in the city centre.
An extremely cold weather front has gripped much of Europe and temperatures have plummeted as low as -20C in Serbia.
Medical charity MSF has treated the first cases of frostbite and is warning of "potentially deadly consequences" if people living out in the open are not given adequate winter shelter.
The official camps are overcrowded and migrants are left with no other options than to sleep in abandoned buildings or out in the open, MSF said.
MSF Humanitarian Affairs Adviser Andrea Contenta, who is in Serbia, told ITV News: "We need to look at the reality, there is nearly 8,000 people stuck in Serbia with no way for them to proceed.
"The conditions are totally inhumane. There are people that have been there for months and months without access to toilets, showers or water."
The Balkan route shut after the EU made a deal with Turkey last year.
Mr Contenta stressed "it is cold every year in Serbia" and it is a lack of long-term planning and political will that is putting these people at risk.
Around 2,000 refugees and migrants are sleeping in abandoned buildings in Belgrade.
Hundreds in the north of Serbia are sleeping rough outside in open fields.
Those who do manage to find shelter in the city are at risk of respiratory infections.
Mr Contenta said: "The freezing conditions mean people are burning whatever they can get their hands on and they sleep in buildings full of smoke. They have been without basic hygiene for months."
Mr Contenta said MSF had been negotiating with officials for months to try and secure safety and resources - such as toilets - for refugees and migrants who are not in the official camps but he said it was refused on the grounds it could attract more people.
MSF say Serbian authorities have severely restricted the provision of humanitarian assistance to unofficial camps and only tolerate volunteers doing a basic distribution of blankets and food.
The country has agreed with the EU to host up to 6,000 people but only 3,140 currently live in facilities adapted to winter, the charity said.
Stephane Moissaing, MSF’s Head of Mission in Serbia, said: "For months, the strategy has been to block humanitarian aid to push these people into official camps.
"But the camps are full and already stretched beyond their capacities, so today migrants are left with no option other than to sleep in abandoned, open buildings in freezing temperatures."
A spokesperson for Human Rights Watch said the situation in Serbia is "clearly unacceptable" and it "goes against Serbia’s obligations under international law".
She said: "The camps are full. The Serbian government has a responsibility to establish decent winterized accommodation."
The UNHCR estimates 82% of the 7,200 refugees and migrants in Serbia are in government shelters.
A UNHCR spokesman said: "Despite the harsh weather, a number of persons sleeping rough in the Belgrade city centre opted not to move to any government shelters.
"Even if not all of them may be considered as persons of concern to UNHCR, as a life saving measure, UNHCR has, in close coordination with the authorities and other partners, including MSF, liaised and organised provision of assistance, such as stoves and additional blankets, winter clothes."
Thousands of refugees are also living in freezing conditions in Greece and France.
In the last week, MSF’s mobile clinic in Paris cared for eight refugees that were found close to hypothermia.
As the temperature fell below zero last week, MSF teams said they witnessed police confiscating blankets from refugees.