Shelter must be found for the thousands of refugees reaching the small holiday island of Kos before trouble breaks out, a UN worker has warned.
Many are sleeping rough on the streets or in make-shift tents with little access to food or water and suffering heat exhaustion while they wait, sometimes weeks, to be registered by police.
The vast majority intend only to pass through tourism-dependent Kos on their way to wealthier countries in Europe but under-pressure officers are struggling to deal with the paperwork creating a bottleneck effect.
Roberto Mignone, the UN Refugee Agency's emergency co-ordinator in Kos, described it as a "fragile situation".
He said: "It's a very serious crisis in Kos.
"Our main concern is for the refugees and migrants but we recognise that it creates a serious problem for the island and to the tourism industry.
"What's unique about here is that there is no accommodation centre here so they are sleeping on the streets with very little support while they wait for their papers.
"We have called many times for a centre so they can wait in a more dignified way but the local and national Greek authorities cannot agree.
"Perhaps there is a feeling that if an accommodation centre is set up more people will come or stay, but the fact is without an accommodation centre people are still coming and they will continue to come.
"I think it is a very serious situation because the number will continue to increase and there could be some incidents which will create trouble.
"It is like two worlds meeting and it is a shock for everybody. Imagine being from a small village in Afghanistan fleeing the war and arriving on a holiday beach with tourists.
"It's a very fragile situation. A solution must be found."
Smuggled on dinghy boats overnight
Around 34,000 migrants have arrived in the small island of Kos alone since January - accounting for around a tenth of all migrants who have reached EU borders in that period, he added.
The majority of the migrants are refugees fleeing war-torn Syria who have already travelled through southern Turkey and into western Turkey before being smuggled on dinghy boats overnight to Kos and other islands in the Aegean Sea.
Those who reach Kos hope to continue on to mainland Greece before travelling north through Macedonia, Serbia, Hungary and beyond, aid agency the International Rescue Committee explained.
A ship chartered by the Greek authorities to act as a make-shift registration centre set sail for Athens today with 2,500 migrants on board, but up to 3,000 are still remain on the island with more arriving every day.
The British Red Cross which is supporting the Hellenic Red Cross in Kos, called on the rest of Europe to share the burden of unprecedented migrant arrivals with Greece.
A spokeswoman said: "It's a huge amount of pressure on an island like Kos to cope with, there needs to be a sharing of responsibility throughout Europe.
"It it's left to geography alone it then it will fall to a few countries like Greece and Italy and that is not fair."
Sleeping rough along waterfront
This morning, more boats from Turkey arrived undetected in the darkness on the northern shore of the island.
Migrants, many of whom appeared exhausted, clambered onto the beach carrying their belongings and even small children.
They walked in groups of up to 20, many of them Syrians, past early morning runners and swimmers to the island's port to join hundreds of others sleeping rough along the waterfront.
A line of tents was punctuated with roughly assembled cardboard shelters along the beach in the shadow of grand yachts, while some were forced to sleep on the pavements with only a thin sheet to lie on.
Mothers nursed small babies and parents covered their children with discarded life jackets in an attempt to keep them warm before the sun came up.
A group of weary Iraqis have been sharing a small tent for nearly two weeks, visiting the police station each day in the hope they could receive their papers and move on.
Tourists disembarking from a passenger ferry looked visibly upset as they walked through the centre of the makeshift camp on their way to their hotels.