Greece said Saturday it has blocked thousands of migrants from crossing its border "illegally" from Turkey, following an influx of refugees fleeing fresh violence in northwestern Syria. Turkish President Recep Tayyip Erdogan said Saturday that his countrys borders with Europe were open, as thousands of refugees gathered at the frontier with Greece. "Greece yesterday came under an organized, mass, illegal attack of violation of our borders and endured it," government spokesman Stelios Petsas said Saturday after an emergency meeting with Prime Minister Kyriakos Mitsotakis. "We averted more than 4,000 attempts of illegal entrance to our land borders." Clashes erupted between Greek police and migrants on the border Saturday, after the influx of refugees following deadly strikes in Syrias Idlib province. Migrants played a cat-and-mouse game with Greek border patrols throughout the night and into Saturday, with some cutting holes in the fence only to be turned back by tear gas and stun grenades. The move by Turkey to open its border, first announced Thursday, was seen in Greece as a deliberate attempt to pressure European countries. It comes as tensions ratcheted up between Turkey and Syria. More than 55 Turkish troops have been killed since Turkey began sending further reinforcements into areas of northwest Syria under the control of opposition factions, which are backed by Turkey. “We will not close the gates to refugees,” Erdogan said in a speech in Istanbul. “The European Union has to keep its promises.” Under a 2016 deal, Turkey agreed to stem the tide of refugees to Europe in return for financial aid. It has since protested that the EU has failed to honor the agreement. Turkey currently hosts more than 3.5 million Syrian refugees, and many fleeing war and poverty in Asia, Africa and the Middle East use it as a staging post and transit point to reach Europe, usually through neighboring Greece. On Saturday, small groups managed to get across into Greece clandestinely. The vast majority were from Afghanistan, and most were men, although there were also some families with young children. They took shelter during the night in abandoned buildings or small chapels in the Greek countryside before starting to walk towards northern Greek. “We learnen the border was open and we headed there. But we saw it was closed, and we found a hole in the fence and went through it,” said Ali Nikad, a 17-year-old Iranian who made it into Greece overnight with a group of friends. Nikad said he had spent two months in Turkey but couldn’t make ends meet, and was hoping to find his uncle who was already in Greece. Many of those who made it across the land border were seen being arrested and driven away in white vans. A police officer told The Associated Press there was pressure along the 200-kilometer (125-mile) land border from migrants trying to force their way through overnight, and groups were being constantly repulsed. Others were making their way to Greek islands in dinghies from the nearby Turkish coast. Greece and Bulgaria increased security at their borders with Turkey. In Athens, Greek Prime Minister Kyriakos Mitsotakis convened an emergency meeting of top cabinet, military and coast guard officials Saturday morning on the issue.