ATHENS, Greece (AP) — Conditions for refugees on Greek islands and in other camps where they are housed in tents despite severe cold weather are "untenable," the European Commission said Monday.

Heavy snowfall has hit large swaths of Greece, including the eastern Aegean islands where thousands of refugees are stranded, with temperatures falling well below freezing. A state of emergency has been declared in some parts of the country.

Giorgos Kyritsis, spokesman for the government's crisis committee on migration, told Greece's Skai television that just under 1,000 people remain housed in tents on the islands.

The severe weather had been forecast well in advance, and the government has come under fire for not acting fast enough to ensure all refugees are adequately housed. Images aired on Greek media have shown tents covered with snow in at least one camp on the island of Lesbos.

The Doctors Without Borders medical aid group has called for the "immediate taking of emergency measures" to ensure proper housing.

"Despite the Greek government's assertions that the relevant measures had been successfully completed, winter preparations for migrants and refugees stuck on Greek islands have failed," the group said.

In Brussels, Commission spokeswoman Natasha Bertaud said the commission was "doing its utmost to support the Greek authorities to address concerns relating to the reception centers and the humanitarian needs on the ground."

"Of course, ensuring adequate reception conditions and managing the refugee centers in Greece is a responsibility first and foremost of the Greek authorities," she added.

Asked specifically about refugees enduring sub-freezing temperatures, she said the commission was "aware that the situation is currently untenable, but we also have to be clear" that conditions in reception centers are the responsibility of Greek authorities. "We can no more dictate policy in Greece than we can in any other member state."

Kyritsis said measures had been taken to move people in northern Greece and on the islands to more suitable accommodation ahead of the weather.

"Despite that, somewhat less than 1,000 people remain in tents" on the islands, Kyritsis said. "Some people there are facing hardship." He added that efforts had been made to move people to hotels, but that some locals had objected. Recently, Migration Minister Yannis Mouzalas had said there were no longer any refugees living in tents in Greece, although he has acknowledged problems on the islands.

In northern Greece, although most people have been moved from camps into hotels and other structures, some remain in tents there as well, refugees say.

"It's very, very cold. We can't survive at night," said Abdu al Mohammed, a Syrian living in the Oraiokastro refugee camp in northern Greece. Camp residents there are housed in tents inside a warehouse. Al Mohammed said that while the camp was being emptied, with people being moved to hotels, about 100 people remained. They were using empty barrels to light fires to keep warm, he said.

Temperatures in the northern city of Thessaloniki have dropped to minus 12 C (10 F) at night over the past few days.

Raf Casert reported from Brussels. Costas Kantouris in Thessaloniki contributed to this report.