ATHENS (AP) — The United Nations refugee agency on Friday pressed Greece to improve conditions at the crowded island camps where thousands of migrants are held as part of a European Union deal with Turkey.

The U.N. agency said in a statement that conditions in the camps, where nearly 20,000 people live, are “squalid, inadequate and rapidly deteriorating.”

UNHCR also urged the Greek government to move more migrants from the eastern Aegean Sea islands to mainland Greece.

Tens of thousands of migrants illegally enter Greece every year from Turkey, hoping to move on to more prosperous European countries.

Under the EU-Turkey deal reached in 2016, they are supposed to be kept on the islands and returned eventually to Turkey. But in practice, most apply for asylum in Greece, while there is a steady flow to the mainland of people Greek authorities designate as members of vulnerable groups.

“UNHCR is particularly concerned about woefully inadequate sanitary facilities, fighting amongst frustrated communities, rising levels of sexual harassment and assaults and the increasing need for medical and psycho-social care,” the agency statement said.

It said conditions were “reaching boiling point” at the Moria camp on Lesbos, where 7,000 people were living in accommodation designed for 2,000.

While, according to the UNHCR, more than 3,000 asylum seekers on the islands have been given authorization to move to the mainland, lack of accommodation facilities there are slowing the process.

Greece’s interior ministry said 49 people reached the islands on Thursday, while 40 others were transferred to the mainland.

Migrants also cross from the land border with Turkey. On Friday, police said seven people were injured when a van carrying 24 migrants crashed on a highway near the border town of Alexandroupolis.

Also Friday, the coast guard said it stopped a yacht with 88 migrants and two suspected traffickers on board off the western island of Cephallonia. The vessel was believed to have been heading for Italy.