Greek police fired tear gas towards migrants who were gathered on the border with Turkey demanding entry as the Syria crisis abruptly moved onto the European Union's doorstep.
The Greek government on Saturday reiterated its promise to keep migrants out as live images from Greece's Skai TV of the border crossing at Kastanies showed Greek riot police firing tear gas rounds at groups of migrants who were hurling stones and shouting obscenities, Reuters reported.
"The government will do whatever it takes to protect its borders," government spokesman Stelios Petsas told reporters, adding that in the past 24 hours Greek authorities had rebuffed attempts by 4,000 people to cross.
About 13,000 people had gathered along the 212km-long (132-mile) border after Turkish officials told MEE on Thursday that Syrian refugees would be allowed free passage to Europe, and then began busing them from Istanbul.
"Thousands of migrants, including families with young children, are passing a cold night along the border between Turkey and Greece," the International Organization for Migration (IOM) said in a statement.
The UN agency said its staff had been tracking the movement of people from Istanbul and were providing humanitarian assistance to the most vulnerable.
By Saturday evening, staff working along the border between Turkey and Greece had observed at least 13,000 people gathered at formal border crossing points and multiple informal border crossings, it said.
The agency said it had spotted "groups of between several dozen and more than 3,000.
"The number of migrants moving… towards the border grew through the day as cars, taxis and buses arrived from Istanbul," according to the head of IOM's Turkey mission, Lado Gvilava.
IOM staff reported that buses continued into the evening to be "loaded to over-capacity" in Istanbul with people bound for the border area.
Turkish President Tayyip Erdogan said on Saturday that about 18,000 migrants had crossed borders from Turkey into Europe. Speaking in Istanbul, he did not immediately provide evidence for that number, but he said it would increase, AFP reported.
Greek police were keeping media away from the Kastanies border crossing, but the broader area, where the two countries are divided by a river, was more permeable.
A group of Afghans with young children waded across fast-moving waters of the Evros River on Friday morning and took refuge in a small chapel.
"Today is good," said Shir Agha, 30, in broken English. "Before, Erdogan people, police problem," he said. Their shoes were caked in mud. It had rained heavily the night before, and by early morning temperatures were near freezing.
MEE reported that the mass movement of people began after Ankara allowed Syrian refugees to travel freely towards Europe as a way to pressure EU governments for assistance in the Syrian conflict.
Turkey and Russia, which back opposing forces in the Syria conflict, have held talks to defuse tensions after an air strike killed 33 Turkish troops in Syria’s Idlib province, sparking fears of a broader war and a new migration crisis for Europe.
About a million refugees and migrants crossed from Turkey to Greece's islands in 2015, setting off a crisis over immigration in Europe, but that route all but closed after the European Union and Ankara agreed to stop the flow in March 2016.
