Migrants trickled through permeable borders to Greece from Turkey on Sunday as thousands gathered on the country's frontier seeking entry after Ankara relaxed curbs on their movement.
At first light, dozens of people in three dinghies made their way to the Aegean island of Lesbos, a Reuters witness said. Further north, groups waded across a river at Kastanies on the shared border.
There was tension at Kastanies on Saturday after riot police used teargas to repel hundreds of migrants on the Turkish side demanding access to Greece.
Turkey has said it will no longer restrain hundreds of thousands of migrants on its territory from reaching Europe, triggering an almost instant rush to the borders it shares with European Union member Greece.
"Yesterday there were 9,600 attempts to violate our borders, and all were dealt with successfully," deputy defence minister Alkiviadis Stefanis told Greece's Skai TV.
The International Organization for Migration put the number of people along the Greek-Turkish border at 13,000. By late Saturday, buses in Turkish cities were still being loaded with people bound for the border area, it said.
Greece was a gateway for hundreds of thousands of asylum seekers into Europe in 2015 and 2016. There are already more than 40,000 migrants on the Aegean islands, living in severely overcrowded camps and filthy conditions.
Last week, clashes broke out on Lesbos between riot police and locals to create closed detention centres to move the existing migrant population. Locals say the islands are suffering a disproportionate burden.
The European Union said it was supporting Greece.
Greece has vowed to keep a mass influx out. "We don't want this influx in our country, this country is not a free-for-all," Migration Minister Notis Mittarachi told Greece's Ant1 TV.
Reuters witnesses saw small groups of people making their way across fields outside the Greek town of Orestiada, close to the frontier. Four young Afghans, looking exhausted, sat around a small campfire.
Further along, Najibe Rezayi, 26, also from Afghanistan, cradled her seven-month daughter in her arms. "We want a place to stay, food, warmth," she said through an interpreter as they walked through mist in frost-covered fields.
Police and the army have been arresting people who attempt to cross into the country.
"They are all Afghans, no Syrians," one army officer said. 
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