Greece's prime minister Alexis Tsipras has conceded that the country is unable to cope with the thousands of migrants arriving daily on its shores, just days after saying he was ashamed by Europe's handling of the crisis.
With at least 430 people having died this year trying to make the short sea crossing along Greece's border with Turkey, Mr Tsipras said it was "imperative" to reach a deal with Ankara to stem the flow.
International aid agency IRC, which has a unit on Lesbos, said conditions at one main centre were unacceptable and that Greece had struggled for years to cope with far fewer migrants.
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Meanwhile, the United Nations refugee agency UNHCR has launched a new funding appeal, saying it needed €88.5 million in additional support for Greece and affected Balkan countries.