What's the story?

Turkey will no longer stop Syrian refugees from attempting to reach Europe, as Ankara scrambles to respond to the killing of 33 of its soldiers by Syrian government forces in Syria's Idlib region. The decision comes as increased fighting between Turkish-backed rebels and Syrian government forces in the last few months has led to the displacement of hundreds of thousands of people from the northwestern region of Syria. Beyond the apparent breakdown of the EU-Turkey migrant agreement, growing tensions between Ankara and Damascus could have a serious geopolitical knock-on effect, with both Russia and NATO looking closely at the situation. 

Read more: Turkish soldiers killed in airstrike in Syria's Idlib amid Russian-Turkish de-escalation talks

What has Ankara said so far?

With the imminent arrival of refugees from Idlib, Turkish police, coastguard and border security officials have been ordered to stand down on refugees' land and sea crossings towards Europe. Turkey's president, Recep Tayyip Erdogan, has repeatedly threatened to open the gates for migrants to travel to Europe, reversing a pledge Ankara made to the EU in 2016. 

In a series of tweets, his top press aide, Fahrettin Altun, accused Syria's president, Bashar al-Assad, of "conducting ethnic cleansing" and seeking to drive millions of Syrians out of Idlib: "These people will try to escape to Turkey and Europe. Already hosting close to four million refugees, we do not have the capacity and resources to allow entry to another million."

Why has Ankara opened its borders now?

Thursday's government airstrike on Turkish soldiers in Idlib has raised the prospect that Ankara will launch a full-scale operation against Syrian government forces. This would significantly increase the number of refugees coming form Syria, where one million civilians have been displaced near the Turkish border since December. The stand-off has created the worst humanitarian crisis in a nine-year war that has already displaced millions and killed hundreds of thousands. The UN has said the fighting in Idlib was having "catastrophic" humanitarian consequences with at least 134 civilians, including 44 children, killed in February and schools and hospitals destroyed.

Read more: Putin, Erdogan agree to mull meeting on Idlib in near future

What is the situation at the EU/Turkish border?

Nearly 300 migrants including Syrians have already arrived in Turkey's western Edirne province on the border with Greece in a bid to go to Europe, according to the Turkish DHA news agency. Another group of migrants arrived on the coast of Ayvacik in Canakkale province, western Turkey, and wanted to go to the Greek island of Lesbos by boats, it reported. Syrians, Iranians, Iraqis, Pakistanis and Moroccans are said to be among those trying to make the journey into the European bloc, with reports of migrants arriving at Bulgaria's borders as well.

How have EU countries responded?

The EU has called on Ankara to uphold its side of the migrant pact, while Greek border guards on Friday blocked hundreds of migrants from entering the country, with Athens increasing security at its sea and land borders with Turkey after the overnight developments. "Greece has tightened the guarding of its borders to the maximum level possible," a government source said, while a police source stated that border patrols had been doubled and a general call for heightened readiness had been issued. Athens is in contact with the EU and NATO on the matter.

Bulgaria is also tightening security along its border with its southeastern neighbor, with Prime Minister Boyko Borissov saying: "We have data about a lot of crowding ... We are tightening maximum control at the border." He also stated he was arranging to talk to Erdogan over the phone. 

What did the EU-Turkey accord involve?

Under the 2016 deal, the EU provided billions of euros in aid in return for Ankara agreeing to stem the influx of migrants into Europe, sending migrants and refugees who cross the Aegean Sea without papers back to Turkey. Ankara, which already hosts 3.7 million Syrian refugees, has said funding from Europe was slow to materialize and paltry next to the $40 billion it has spent, and has repeated it cannot handle taking in more Syrians, with popular discontent already growing against their presence.

What is happening on the Greek islands?

Greece is already struggling to accommodate thousands of asylum seekers stranded in the country for the past five years, especially on its islands, where migrant camps are stretched far beyond capacity, with more than 38,000 migrants crowded into camps on Lesbos, Chios, Samos, Leros and Kos. Only a few hundred migrants have been sent back to Turkey and just a handful of European states have offered to accept refugees from Greece after EU borders were shut in 2016.

How is Greece handling the renewed migrant influx?

The conservative government of Prime Minister Kyriakos Mitsotakis, which came to power in July, has failed to persuade Greek island authorities to accept the creation of new camp facilities. Camps on the Greek mainland are also full and local authorities there also oppose efforts to relocate additional asylum seekers. Earlier this week, the government tried to push forward with its camp plans by sending riot police and construction machinery to Lesbos and Chios. But after days of violent skirmishes with local protesters that left dozens injured, the police were pulled back on Thursday.

What is the situation in Syria?

Turkey said it has retaliated to Thursday's attack by hitting more than 200 Syrian government targets in drone and artillery bombardments, with the reprisals reportedly killing 16 Syrian soldiers. Moscow in turn has announced that two of its warships were transiting through the Bosphorus Strait in Istanbul in plain sight of the city. 

Ankara also called on the international community on Friday to establish a no-fly zone over Idlib, where Syrian government forces have taken back areas of the region since December. Elsewhere, Turkey-backed rebels and militants on Thursday re-entered Saraqeb, a key Idlib crossroads town they had lost earlier in February, reversing one of the main gains of the government's offensive.

How has the international community responded?

In a move to try to defuse the crisis, Russia's president Vladimir Putin and his Turkish counterpart Erdogan spoke by phone on Friday, with Russia's foreign minister Sergei Lavrov stating: "There is always room for dialogue." The U.S. State Department responded by saying Washington stood by its NATO ally and continues to call "for an immediate end to this despicable offensive by the Assad regime, Russia and Iranian-backed forces."

NATO held urgent talks on the crisis on Friday, and joined the UN, U.S., and EU in calling for urgent de-escalation, with EU foreign policy chief Josep Borrell saying: "There is a risk of sliding into a major open international military confrontation." He added: "It is also causing unbearable humanitarian suffering and putting civilians in danger."

UN spokesman Stephane Dujarric reiterated Secretary General Antonio Guterres's call for an immediate ceasefire, saying: "Without urgent action, the risk of even greater escalation grows by the hour."