German chancellor Angela Merkel and other EU leaders have criticised Turkey's warning that "millions" of migrants are headed to Europe.
Turkish President Recep Tayyip Erdogan warned on Monday that "millions" of migrants will soon head for Europe, drawing a sharp rebuke from EU leaders over his efforts to pressure them into greater assistance with the Syrian conflict.
Since Turkey "opened its doors" on Friday for refugees and migrants to leave for the European Union, thousands have massed at the Greek border, triggering fears of another influx like that which poisoned European politics in 2015.
German Chancellor Angela Merkel described Turkey's move as "unacceptable", while EU migration commissioner Margaritis Schinas said "no one can blackmail or intimidate the EU".
But Turkey, which already hosts some four million refugees, is trying to hold off another mass influx from Syria where regime forces, backed by Russian air power, are advancing into the last rebel stronghold of Idlib.
Mr Erdogan said he hoped for a ceasefire in Syria when he meets his Russian counterpart Vladimir Putin later this week.
But he warned Europe that it would share the migrant pressure.
"After we opened the doors, there were multiple calls saying 'close the doors'. I told them 'it's done. It's finished. The doors are now open. Now, you will have to take your share of the burden'," he said.
Mr Erdogan claimed the numbers of migrants at the Greek border, who include Afghans, Syrian and Iraqis, were far higher than figures provided by officials and reporters at the scene. He said there were already hit "hundreds of thousands" there.
"There will be more. Soon, this number will be expressed in millions."
Greece says some 10,000 were barred from entering the country over the weekend.
Clashes broke out as police fired tear gas at the refugees who responded by lobbing rocks.
A video shared by a Turkish official, which could not be independently verified, showed a boat of migrants being shot at and harassed by Greek coastguards.
Turkey also accused Greek police of killing a migrant after a video was shared of a bloodied Syrian on the border, although Athens rejected this as "fake news".
In desperation, many have sought alternative routes and Greek port police said a young boy died when a makeshift boat capsized off the Greek island of Lesbos.
Athens said it would boost patrols and it suspended asylum applications by those entering illegally -- a move denounced by the UN refugee agency as having "no legal basis".
Turkey agreed in 2016 to stop refugees leaving for Europe in exchange for billions of euros in assistance, and the EU insists that Turkey stick to the deal.
Ceasefire in Idlib?
The migrant question comes as Turkey has launched a military operation in Idlib in northwestern Syria in a bid to push back the regime's offensive.
Close to one million people have been forced to flee the regime's assault in the biggest wave of displacement of the nine-year conflict, but they are not being permitted into Turkey.
Mr Erdogan and Vladimir Putin will meet in Moscow on Thursday.
Despite being on opposing sides of the conflict, they will be keen to avoid direct clashes that would jeopardise their broader trade and defence ties.
"I hope that he (Mr Putin) will take the necessary measures there, such as a ceasefire, and that we will find a solution to this affair," Erdogan said in a speech Monday.
The Kremlin said cooperation with Turkey was a top priority.