Pazarkule (Turkey) (AFP) - Greek police fired tear gas in clashes with migrants at the Turkish border on Friday, as Athens said a 2016 EU-Ankara deal limiting migration to Europe was "dead".

Thousands of people have gathered at the border since Turkish President Recep Tayyip Erdogan said last week that his country would no longer stop refugees from trying to leave.

Greece's Prime Minister Kyriakos Mitsotakis accused Ankara of "assisting" an ongoing surge of desperate people gathering at the border.

"Right now, let's be honest, the agreement is dead," Mitsotakis told CNN, referring to the EU-Turkey accord.

"And it's dead because Turkey has decided to completely violate the agreement, because of what happened in Syria," he added.

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

Mitsotakis said Turkey was doing "the exact opposite" of its obligation to hold back asylum-seekers.

- 'Open the gates' -

Friday's brief clashes occurred as migrants tried to break through the fence, according to AFP journalists at the scene, but they quickly ended the volley of rocks and instead sat peacefully chanting "freedom" and "open the gates".

Greek forces say they have prevented nearly 39,000 people from crossing the border. Turkey claims the real number is more than three times higher.

Many migrants say they are being pushed to attempt illegal entry to Greece.

"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 EU's diplomatic chief made a direct appeal to the migrants not to go to the Greek border.

"The border is not open," EU High Representative Josep Borrell said after a meeting of EU foreign ministers in Zagreb.

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Turkey and Russia agreed a ceasefire in Syria on Thursday, but Ankara is still threatened by a potential new influx of refugees from the last rebel stronghold of Idlib and has sought to pressure Europe into providing greater assistance.

Turkey already hosts some four million refugees, and recent advances by the Syrian army, backed by Russian army, have pushed close to a million more towards its border.

Later Friday, the Greek government released footage which it said showed Turkish riot police firing a tear gas barrage at Greek border guards.

It came after the release of separate footage from Turkish state TV TRT which it said showed asylum-seekers stripped and beaten by Greek forces.

A Greek police source disputed the claim, telling AFP: "We are not letting them through the border, so how can we be doing that to them?"

Ankara has officially accused Athens of using undue violence against asylum-seekers, killing several and injuring many. Greek officials have repeatedly dismissed this as untrue.

- 'Coordinated attacks' -

Earlier Friday, Greek officials accused Turkey of 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."

Meanwhile, two Greek men were convicted of threatening aid workers on the island of Lesbos, where there has been a violent backlash against those helping the swelling number of arrivals.

"I will continue to defend my country. Most of the (aid groups) operate like spies. These gangsters should leave the island," said 73-year-old Konstantinos Alvanopoulos after being given a three-month suspended sentence.

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.

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 EU welcomed the ceasefire.

"For sure I am pleased for the ceasefire, the ceasefire is good news. At least it's goodwill -- let's see how it works," Borrell said 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.

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