World Vision has joined in calls for EU leaders to protect children who are among refugees and migrants fleeing war-torn nations and are now caught in freezing conditions in Europe and the Middle East.

The organisation says hundreds of refugees from countries including Syria, Iraq, Afghanistan and Pakistan are living in "miserable" conditions in makeshift camps and abandoned warehouses in Serbia as temperatures fall as low as minus 20 degrees Celcius. It cites UNHCR estimates that more than 6,400 refugees and migrants are stranded in Serbia due to border closures.

Justin Byworth, World Vision's Brussel's executive director, says "now more than ever", European leaders need to work together on a joint response.

“They have the opportunity and the power to prevent unnecessary suffering," he said. "They need to stand by countries of first entry, like Greece, so they don’t have to shoulder on their own all the responsibility for managing overcrowded reception sites."

He said that to date fewer than eight per cent of the 106,000 refugees that the EU had agreed to relocate from Greece and Italy to other member states have been transferred.

"That’s not enough," he said. "The EU has promised to relocate people from the Greek islands, but there are still hundreds of children trapped in unbearable conditions. Leaders need to step up and take urgent action, and recognise that everyone has a part to play."

World Vision is among 28 aid agencies that are calling for greater action.

Last week UNICEF said that an estimated 23,700 refugee and migrant children remain stranded in Greece and the Balkans with the cold weather meaning they are vulnerable to respiratory illnesses and even death from hypothermia.