EU President Donald Tusk called Thursday on migrants heading to Europe for economic gains to stay away, as some among the thousands of people stranded in northern Greece demonstrated to have borders opened further along their route.
"I want to appeal to all potential illegal economic migrants, wherever you are from: Do not come to Europe," Tusk said after meeting Premier Alexis Tsipras in Greece as part of a tour of countries worst affected by Europe's migration crisis.
"Do not believe the smugglers. Do not risk your lives and your money. It is all for nothing," Tusk said, warning that migrants will no longer be simply waved through from country to country.
Europe has struggled to get under control the migrant flows, which stretch from Turkey to Greece and through the Western Balkans to wealthy northern European countries such as Germany or Sweden.
More than 1 million people reached European shores last year. Many were fleeing conflicts in the Middle East and have the right to apply for asylum in the European Union. But economic migrants who do not qualify for international protection have also joined their ranks.
Thousands of people have now started massing at the Greek border to Macedonia as countries along the so-called Balkan migration route have largely been shut down by migration restrictions.
Hundreds of Syrian and Iraqi refugees protesting the closure of the route to Northern Europe blocked a train track on Thursday near the Macedonian border at the northern Greek village of Idomeni, while chanting "open the border."
Officials estimate that 12,000 to 15,000 people needing urgent humanitarian assistance are in the area around Idomeni, waiting for permission to continue their journey. But Macedonian authorities are letting through fewer than a couple of hundred a day.
As many as 70,000 people could be stranded at the border by the end of the month, Greek officials have said.
During his visit, Tusk promised that the EU will not abandon Greece and its people, which he said are "paying a very high price for a problem they themselves did not create."
Tusk has been trying to convince countries affected by migration to join forces in a European response to the crisis, rather than acting unilaterally.
"Unilateral decisions without prior coordination, however understandable they are in a national context, are in fact detrimental to the European spirit of solidarity," he said.
Greek Prime Minister Alexis Tsipras said he would demand at a special migration summit in Brussels on Monday that sanctions be brought against those EU countries that are not implementing decisions jointly taken by the bloc in response to the crisis.
Tusk was expected later Thursday in Turkey, for two days of talks with Prime Minister Ahmet Davutoglu and President Recep Tayyip Erdogan. The country is to participate in Monday's migration summit.
Top officials from the European Commission were also in Turkey on Thursday.
The EU's executive is to present on Friday a report on the "concrete steps needed to return order to the management of the EU's external and internal borders," commission spokesman Margaritis Schinas said.
He declined to comment on its content, but the German daily Sueddeutsche Zeitung reported that the commission has prepared a roadmap which foresees the migration-related border controls instituted within the EU to be lifted by the end of the year.
This would be achieved by Greece receiving assistance from the EU border agency Frontex to secure its border with Turkey and by a new European border and coast guard being put in place by autumn.
The Sueddeutsche Zeitung reported that, according to commission estimates, the internal border controls come at a cost of 7 to 18 billion euros (7.6 to 19.6 billion dollars) per year for the European economy, which usually enjoys free movement of people and goods.