The United Nations Children’s Fund (UNICEF) said two-thirds of the nearly 3,000 unaccompanied refugee and migrant children currently in Greece are not receiving proper shelter and care.

“Children stranded without families should have proper shelter, care and protection, and there are solutions that could make this a reality for them,” Laurent Chapuis, Country Coordinator for UNICEF’s refugee and migrant response in Greece said in a statement.

He said the answers are to transfer these children to shelters on the mainland without delays, devote available funding to existing shelters with the right standards, and put more foster care or supervised living schemes in place.

Greece’s migration minister Yiannis Mouzalas has refused to let some 14,000 refugees and migrants on the islands near Turkey to come to the mainland where there are another 50,000 in detention centers and camps.

Human rights groups have criticized conditions in those facilities although UNICEF said Greece has made some strides in improving the facilities.

In September, there were more than 5,700 arrivals in Greece compared to an estimated 3,080 arrivals a year earlier, stepping up tension in the camps and centers where there has been violence as Greece has tried to deal with an overwhelming number of asylum applications.

There are now some 1,800 unaccompanied children waiting for a place in shelter, living in open sites, reception centers, or who are otherwise stranded on the islands or in de facto detention centers. Some of these children are even living on the streets, and the approaching winter is adding to the risk.

Children are particularly vulnerable at night without proper safeguards in place. Delays of up to five months in transferring children from the islands to the mainland are compounding their emotional and mental strain, the agency said.