The UN refugee agency on Thursday warned of mounting tension on Greek islands holding thousands of refugees and migrants, calling for more transfers to the mainland.
"On the islands the situation has become a bit more tense with additional arrivals... Lesbos, Samos and Chios is where the situation is the most tense," Philippe Leclerc, the UNHCR representative in Greece, told reporters.
"We need additional places... we need more support on the ground and to have more transfers from the islands to the mainland," Leclerc said.
The call came as the EU announced an accommodation initiative to help relieve some of the strain.
Leclerc said over 8,000 people had been transferred to the mainland "lawfully", there is no indication of how many more crossed with the help of smugglers, but more needed to be done.
Earlier on Thursday, hundreds more had landed on Lesbos and Samos from neighbouring Turkey, he said.
According to government figures, camps on Lesbos, Samos and Chios nominally built to house some 5,500 people are currently accommodating over 9,000.
Many of them are entitled to refugee status, and eventual relocation to the mainland, but the system has bogged down owing to thousands of asylum applications from economic migrants hoping to delay deportation.
Some of the camps have recently seen clashes between police and mainly African migrants who face deportation to Turkey after a long, fruitless wait for asylum.
At the same news conference, EU humanitarian aid commissioner Christos Stylianides unveiled a plan worth $176 million in cash assistance and subsidised rent for 22,000 asylum seekers, mainly in mainland Greece.
"The aim of these new projects is to get refugees out of the camps and into everyday accommodation and help them have more secure and normal lives," Stylianides said.
Eventually the programme, which includes prepaid cash cards for everyday purchases, will benefit 30,000 people by the end of the year, he added.
"This will enable (Greece) to shut down more camps," Stylianides said.
Some 2,000 of the asylum seekers will be given rented accommodation on the islands.
"Infrastructure on the islands needs to be improved," said EU migration commissioner Dimitris Avramopoulos. "And preparation must begin for the winter period."
Greece has already shut down six of 43 camps, Greek Migration Minister Yiannis Mouzalas said.
He added that the Greek state will gradually replace non-governmental organisations in running the camps on the islands.
Overall, the European Union has mobilised over 1.3 billion euros support through to 2020 to help Greece manage migration and the external borders, through various kinds of funding, officials said.