Brief clashes broke out at Turkey's border with Greece on Friday, where thousands of refugees have been encouraged by Ankara to leave for the European Union. 

Greek police fired tear gas at migrants trying to break through the fence, who responded by throwing stones, according to AFP journalists at the scene.

Calm was quickly restored, with hundreds of migrants sitting peacefully in front of the gates, chanting "peace", "freedom" and "open the gates".

Makeshift camps for thousands of migrants have sprung up around the border since Turkish President Recep Tayyip Erdogan said last week they would no longer be stopped from trying to leave the country.

Many say they are being pushed to leave. 

"They (the Turkish military) told us that if you don't go to the border... you will be forced to come back to Turkey and people don't want to come back because they don't have any good opportunities, there isn't anything," Ali, an Iranian, told AFP.

The clashes came a day after Turkey and Russia agreed a ceasefire in Syria following a months-long assault by Damascus on the last rebel stronghold, which has created another huge wave of refugees heading northwards. 

Turkey, which already hosts some four million refugees, said the ceasefire did not change its need for greater assistance in dealing with the humanitarian crisis triggered by the Syrian conflict and other crises in the region.

It backs some of the rebel groups in Idlib and declared a military operation last week in a bid to stop the Syrian advance, which has displaced close to a million people.

On Friday, Greek officials accused Turkey of firing tear gas and smoke bombs at their border guards and providing cutters to migrants to break through fencing. 

"There are coordinated attacks this morning," a Greek official told AFP. "Apart from intimidation, these attacks are taking place from the Turkish police to help migrants cross the fence border line."

'Non-compliance'

Erdogan's office said the Syrian ceasefire would not alter its policy on refugees leaving for Europe. 

"The Russia-Turkey agreement does not... change the fact of the European Union's non-compliance with its promises as part of the 2016 refugee deal," presidential sources told state news agency Anadolu. 

Turkey agreed in 2016 to stop letting migrants leave in exchange for six billion euros -- but Ankara says other parts of the deal including improved visa and trade rules were never fulfilled. 

Russia, which backs Syrian government forces with air power, agreed to impose a ceasefire in Idlib from midnight and the skies were free of warplanes for the first day in months on Friday, although previous peace agreements have proved temporary. 

The ceasefire was welcomed by the EU's top diplomat. 

"For sure I am pleased for the ceasefire, the ceasefire is good news. At least it's goodwill -- let's see how it works," Josep Borrell said as he arrived for talks on the migration issue with EU foreign ministers in Zagreb.

"But there's still an extraordinary humanitarian challenge that I think we all face in terms of the sheer numbers of refugees," added Irish Foreign Minister Simon Coveney.