The Greek island of Kos was the scene of further unrest on Saturday, as migrants desperate to get off the island fought each other in the searing heat.
A passenger ship chartered to house and process refugees lay empty, 24 hours after it had arrived, as the migrants fought to board.
Authorities in Greece have said that the Syrians will be allowed to board, as they are classed as refugees. The Pakistanis, Afghans and Iranians - whose status is less clear cut - reacted by scuffling outside the police station as the riot police looked on, throwing stones and trading punches.
To rival chants of "Afghanistan!", "Pakistan!" and "Iran!", fists and stones flew.
At least one man was kicked on the ground, while others wandered around with blood on their faces. Later, a group of Iranians tried to break the police line blocking access to the police station.
The riot police beat back the crowd with batons during the brief affray.
Tensions have been high on the island since the wave of migrants - mainly Syrian and Afghan refugees - began arriving in the early summer. Greece has now overtaken Italy as the most popular landing spot in Europe, with the United Nations refugee agency UNHCR saying that 124,000 had landed on Greek islands this year. A total of 98,000 have arrived in Italy.
Last week the UNHCR called conditions for migrants on Kos and other islands "shameful", and said about 3,000 migrants and refugees were waiting to be registered by police.
"While they wait, they have to endure inadequate living conditions and little or no assistance," said William Spindler, UNHCR spokesman in Geneva. "There is a great deal of frustration and rising tensions. We call on the Greek authorities to renew their efforts to provide decent reception conditions to refugees arriving in Greece."
On Tuesday a crowd of migrants waiting to be registered were sprayed by police with fire extinguisher foam, causing the crowd to panic and dart through the streets. The images went around the world, causing immense harm to an island which depends heavily on tourism.
Athens responded by sending in squads of riot police on Wednesday. But, with hundreds of migrants making the short boat crossing from Turkey every day, they appeared powerless.
The coast guard in Kos said it had rescued 212 people on the island's northeastern coast on Saturday, who were in four inflatable dinghies and one speedboat.
"This situation on the island is out of control," said Giorgios Kyritsis, mayor of Kos, on Tuesday. "There is a real danger of uncontrollable situations. Blood will be shed."