Thousands of migrants had gathered Saturday at the border post of Kastanies, where some 500 soldiers and Greek police officers sporadically fired tear gas to prevent them entering the EU from Turkey.
Turkey announced on Friday that it would leave its borders with the European Union open to migrants. Since then, Greek soldiers and police have stepped up their patrols along the Evros River, loudly warning of the entry ban.
But the area is large and difficult to watch. Greek authorities use drones to try to locate groups of migrants walking near the invisible line and monitor their progress.
At the border post of Kastanies, some 4,000 migrants and refugees gathered behind the fences, according to a Greek police source, against 1,200 the day before.
Some have climbed trees, others have broken concrete which they throw on the Greek side, others still launch tear gas canisters over the barbed wire.
On the spot, Panagiotis Harelas, president of the Greek border guards, showed the media some of these Turkish-made grenades: "We face Turkish propaganda and Turkish tear gas grenades", he said.
On the secondary roads close to the border, groups of refugees walk tirelessly, some have lost their shoes in the river, they are soaked and covered in mud, exhausted by hours of walking in the cold and in the rain.
They are looking for a way to reach Thessaloniki, the country's second city, a three-hour drive away, or Athens, hoping to contact representatives of the United Nations.