Hundreds of child refugees in Serbia face freezing to death as temperatures plummet to -16C, Save the Children has warned.

Many of the children, some as young as eight years old, have no gloves or proper shoes, and several refugees have already suffered frostbite in the perishing conditions, the charity said.

Up to 2,000 refugees living in makeshift shelters in the Serbian capital of Belgrade are at risk, with some lighting indoor fires to keep warm, resulting in migrants suffering respiratory problems from the toxic smoke.

“Conditions are truly gruesome, these buildings don't have heating, windows, toilets, they don't have water,” Tatjana Ristic, spokesperson for Save the Children Serbia, told The Independent.

“The numbers sleeping rough in Belgrade and squatting in buildings behind the train station started to grow in 2015 and at the moment, this could be the biggest unofficial refugee camp in Europe.”

Ms Ristic said up to 300 children were facing perishing conditions in the camps, many being unaccompanied minors who have already faced unimaginable hardship leaving their home countries.

“Some of these children are very young - nine years old. One boy I met travelled with his uncle who is 15 years old from Afghanistan. They were sleeping in a tent with two friends - one 10-year-old and one 11-year-old,” she said.

According to the charity, up to 100 migrants arrive in Serbia each day, with children accounting for up to 40% of new arrivals.

The migrants are arriving on the Balkans Route, which was officially closed in March 2015 but remains in active use by those hoping to make it to Europe.

More than 61 people – including several refugees and migrants - have reportedly died across the continent as a result of the Arctic weather, with children and babies being particularly vulnerable to hypothermia without proper access to heat and shelter.

“The EU’s continued failure on the refugee crisis is leaving thousands of people, including lone children, literally out in the cold," Kirsty McNeill, Save the Children's campaigns director, said.

"The lack of political will to offer asylum or reunify separated children and families, means these human beings, who have survived years of war, violence and deadly journeys to safety - are now freezing to death on Europe’s doorstep.”