ATHENS, Greece (AP) — Europe's top official for migration on Wednesday deplored the plight of thousands of refugees and other migrants in camps on Greece's eastern Aegean island of Lesbos who face harsh winter conditions.

Dimitris Avramopoulos, the European Union's commissioner for migration, said solutions must be found immediately.

"We all ... have a humanitarian imperative to alleviate the situation here on the islands," Avramopoulos said during a visit to Lesbos, accompanied by Greece's migration minister.

"It simply cannot be that refugees are left out in the cold, to brave the worst of winter without a roof over their heads," Avramopoulos added.

More than 5,000 people live in overcrowded camps on Lesbos, and hundreds had to be evacuated from tents covered by snow during a cold spell this month. Many were transferred to a Greek naval vessel.

Resentment is rising among many Lesbos residents, who have borne the brunt of Europe's immigration crisis for the past two years and fear their tourism-reliant island will remain an open prison for migrants indefinitely.

More than 62,000 refugees and other migrants have been stuck in Greece since a series of Balkan border closures and an EU-Turkey deal on stemming migration.

These include about 15,000 who reached the eastern islands after the March 2016 agreement, and are not allowed to travel to the mainland unless they successfully apply for asylum. If they cannot prove that they merit asylum in Greece, rather than neighboring Turkey from which they traveled, they face being returned to Turkey.

Avramopoulos promised to reduce congestion in island camps by moving vulnerable people to the mainland and stepping up returns to Turkey.

Also Wednesday, the Human Rights Watch organization charged that Greek authorities, as well as the United Nations refugee agency and international charities receiving significant funding to operate Greece's camps, are failing disabled migrants.

"Asylum-seekers and other migrants with disabilities have particular difficulties getting basic services such as shelter, sanitation, and medical care, and ... have limited access to mental health care," the group said. "For example, one older woman who uses a wheelchair had not been able to take a shower for a month."