Greek Interior Minister Panagiotis Kouroublis has compared conditions at refugee camp on the border with Macedonia to a Nazi concentration camp and blamed European countries for closed border policies.
The remarks from Greece came as the EU leaders were meeting in Brussels with the purpose to reach a deal with Turkey on the migration crisis.
"I do not hesitate to say that this is a modern-day Dachau, a result of the logic of closed borders," Kouroublis said reporters at the squalid Idomeni camp.
"Whoever comes here takes several blows to the stomach," he added.
Heavy rains turned the Idomeni camp into a quagmire where thousands of refugees sleep in tiny tents in muddy fields. Dozens of children suffer from colds and fevers and thousands of people wait for hours in long queues to get food handouts from aid groups.
According to the Greek government, at least 46,000 refugees are blocked in the country as Macedonia, Austria and many Balkan countries shutdown their borders.
More than 12,000 refugees, most of whom are children from Iraq and Syria, are in Idomeni camp, which has a capacity of 2,500 people.
In a bid to avoid further overcrowding, hundreds of refugees who landed from the Greek islands at Piraeus on Friday were boarded on buses and sent to relocation camps near Ionnina, northwestern Greece.