Greece is locking hundreds of migrants in an overcrowded centre on the Mediterranean island of Lesbos without proper sanitation and medical care in what French charity Medicins Sans Frontiers branded a "humanitarian crisis".
The migrants, most of them from war-torn Afghanistan, are kept in rooms clogged with stagnant water and only allowed outside for half an hour every couple of days, said Yiorgos Karayiannis, head of MSF Greece's migrant assistance programme.
With some migrants suffering from tuberculosis and skin diseases, there is a risk of contagion and only one doctor was working at the camp, without a translator, MSF said, adding its staff was not being permitted regular access to provide healthcare.
"The situation is horrible from a medical point of view," Karayiannis told Reuters today. "This is an urgent humanitarian crisis."
The Greek government was not immediately available to comment.
The number of the people at the camp has risen from 150 in early June to around 800 at present, Karayiannis said, as calm seas encouraged a deluge of would-be migrants to set off in boats from the nearby coast of Turkey or North Africa.
Greece is on the frontline of the European Union's fight against illegal migration. Its 14,900-kilometres (9,258 miles) of poorly patrolled Mediterranean coastline offers a tempting target for migrants from Iraq and Palestine, Somalia, Pakistan and Afghanistan.
Despite the rising numbers at Lesbos, Greece's conservative New Democracy government has not improved facilities, aid workers say.
MSF has been working at the Lesbos camp for two months, providing some medical attention and constructing toilets and shower facilities. Most of the migrants are young men but there are also some women and children, Karayiannis said.
An estimated 800,000 Albanians have also emigrated to Greece in search of better-paid work. Prime Minister Costas Karamanlis has called for more EU cooperation in fighting immigration.
Migrants are held at the Lesbos centre - one of six such sites in Greece - for up to three months before being given one month to leave the country.
Some drift to Athens, but most use Greece as a springboard to reach richer European countries like Italy, Karayiannis said.
A French plan to boost immigration patrols and expel more migrants from the 27-nation bloc, while promoting legal migration and a common asylum policy, is expected to be approved by mid-October.
"European policy is mainly to guarantee high standards of preventing immigration, but people arriving need to have better facilities available to them and a better future," he said.