Snow covered Europe and plunged much of the continent into sub-zero temperatures this week, making life for the most vulnerable populations even more dangerous.

Thousands of refugees in countries like Greece and Serbia are stranded, either waiting their turn to apply for asylum or hoping for another chance to sneak across a border and head west. Many live outdoors in tents or decrepit warehouses with no heat or electricity.

Aid organizations did not mince words in their disgust at ongoing European inaction on the migrant question.

The inclement weather “is putting their lives in danger,” Stefano Argenziano, a Doctors Without Borders operations coordinator on migration, said in a statement. “We are witnessing the most cruel and inhumane consequences of European policies, which are being used to deter and victimize those who are only seeking safety and protection in Europe.”

Several thousand refugees are still stuck in outdoor camps on various Greek islands despite repeated calls from the U.N. Refugee Agency to move people into facilities on Greece’s mainland, where the organization says more sophisticated infrastructure is in place.

On Wednesday, the Greek government docked a ship off the shores of Lesbos island that is offering shelter to a few hundred people, the International Rescue Committee said in a statement, but it’s “not an adequate long-term response.”

“The world’s most vulnerable people are being punished for seeking sanctuary,” IRC regional representative for Europe Elinor Raikes said in the statement. “Surely they have been through enough already?”

And more than 7,500 people are currently stranded in Serbia, where they are also being housed outdoors in camps or in abandoned warehouses, according to MSF. Children, many of whom are traveling alone, are at risk of dying from hypothermia, the IRC said.

Check out the photos below for a glimpse of the conditions people are enduring:

Yannis Behrakis / Reuters A stranded Syrian refugee braves a snowstorm at a refugee camp north of Athens, Greece.

Yannis Behrakis / Reuters Socks that belong to stranded refugee children are covered in snow.

Nicolas Economou/NurPhoto via Getty Images A refugee in the Softex camp, located in northern Greece, tries to stay warm.

STR via Getty Images Conditions are no better in the Moria camp located on Lesbos island.

Nicolas Economou/NurPhoto via Getty Images People are living outdoors in freezing temperatures.

Nicolas Economou/NurPhoto via Getty Images Some in Softex made the most of the snow.

Nicolas Economou/NurPhoto via Getty Images Tents in Softex are covered in snow. People have no protection from the cold.

Nicolas Economou/NurPhoto via Getty Images Water sources froze, halting the flow of water in the Softex camp.

ANDREJ ISAKOVIC via Getty Images In Belgrade, Serbia, a migrant receives a hot meal in sub-zero temperatures outside of a derelict warehouse being used to shelter migrants.

Anadolu Agency via Getty Images A welcome distraction from the cold.

Anadolu Agency via Getty Images Inside the Belgrade warehouse, where people are huddled under a mountain of blankets.

Anadolu Agency via Getty Images Standing in line for food.