The UN Refugee Agency (UNHCR) urged Greece on Friday to increase efforts to address “alarming” overcrowding and precarious conditions for asylum seekers and migrants staying on the five Aegean islands of Lesbos, Chios, Samos, Kos and Leros.

“UNHCR has been appealing to the Greek government to use emergency measures to expedite its plans to transfer a greater number of asylum-seekers to appropriate accommodation on the mainland,” said UNHCR spokesman Andrej Mahecic at a regular UN briefing.

The agency said that more than 36,000 asylum seekers were currently staying in reception centers across five islands initially designed with a capacity of 5,400.

It said Greece had been “generous and compassionate towards refugees, despite a very complex and difficult situation,” noting that the east Aegean islands had shouldered a disproportionate burden and responsibility.

“It is critical that other regions in Greece step up their solidarity to help alleviate pressures by receiving transferred asylum seekers and opening up reception places,” said Mahecic.

UNHCR said continued European support in terms of resources, capacity and solidarity were also needed to boost Greece’s response.

On Samos, 6,782 people are staying in a center designed for 660, while others reside in makeshift shelters pitched in surrounding fields.

Moria, a town on Lesbos, is hosting 18,342 inside a facility for 2,200 and others are staying in adjacent olive groves.

Reception centers on Chios, Kos and Leros are also overcrowded, said UNHCR.

Families make up the majority of the asylum-seekers and migrants, a third of whom are children, most below the age of twelve.

Thousands of women, men and children who currently live in small tents are exposed to cold and rain with little or no access to heating, electricity or hot water.

Hygiene and sanitation conditions are unsafe, with health problems on the rise, said UNHCR, adding that despite the dedication of medical professionals and volunteers, many were unable to receive medical attention as there were not enough doctors at reception centers and local hospitals.

“Longer-term solutions and improvement of conditions on the islands are necessary but will only be possible once the overcrowded centers are decongested,” said Mahecic.