An airstrike in Syria’s Idlib province on Thursday killed at least 33 Turkish soldiers and wounded numerous others. The attack was a serious escalation of hostilities and the worst loss of life for Turkish forces during their invasion of Syria.

Both Syrian and Russian air forces were blamed for the attack, with Moscow on Friday claiming that Syrian planes carried out the bombing.

Turkish Defense Minister Hulusi Akar said on Friday that Russian officials were told Turkish troops would be operating in the area and should have passed that information along to their Syrian clients. He said Turkish positions were nevertheless hit by repeated bombing runs during the attack.

“Despite warnings after the first strike, the Syrian regime, unfortunately, continued its attacks, even targeting ambulances,” Akar said.

The Russian Defense Ministry responded by accusing Turkish soldiers of “being where they should not have been” and mingling with terrorist forces that were legitimate targets for Syrian airstrikes.

“Turkish soldiers who were in the battle formations of terrorist groups came under the fire of Syrian troops,” the Russians said.

The attack appears to have been prompted by Turkish-backed Syrian rebels recapturing the key town of Saraqib from the Syrian military on Thursday, the first major reversal suffered by the Syrian regime’s latest offensive in Idlib since Turkey began directly supporting the rebels a few weeks ago. Damascus was on track to reclaim over half of the province before the rebel counterattack in Saraqib.

Turkey claims its troops were deployed to Idlib to protect civilians from attacks by the Syrian regime and its allies. Turkey renewed its accusations of “ethnic cleansing” against the Syrian government on Friday and criticized the international community for remaining silent in the face of crimes against humanity.

“Millions of civilians have been bombarded from the air for months now. Infrastructure, including schools and hospitals, is being targeted by the regime systematically. A genocide is happening slowly before our eyes. Those of conscience and dignity must speak up!” said Turkish presidential spokesman Fahrettin Altun.

According to Defense Minister Akar, Turkish forces retaliated for the attack by hitting over 200 Syrian regime targets in Idlib with ground fire and airstrikes.

“After the treacherous attack, more than 200 regime targets were put under heavy fire with our aircraft, armed drone and ground fire support vehicles,” he said.

“Turkish forces destroyed five Syrian regime choppers, 23 tanks, 10 armored vehicles, 23 howitzers, five ammunition trucks, a SA-17, a SA-22 air defense system as well as three ammunition depots, two equipment depots, a headquarter and 309 regime troops,” Akar claimed.

Turkish President Recep Tayyip Erdogan convened an emergency security meeting in Ankara after the attack, then contacted Russian President Vladimir Putin on Friday to discuss the situation. Erdogan and Putin reportedly agreed during the phone call to implement new measures to reduce tensions and agreed to schedule a high-level meeting on Idlib province in the near future.

Erdogan and his spokespeople gave little indication they were satisfied by his talk with Putin. Erdogan’s office said the emergency security council “agreed to retaliate against the illegitimate regime which has turned its barrel against our soldiers who are on duty to protect the rights and interests of the Republic of Turkey.”

Turkish Vice President Fuat Oktay issued a statement vowing that Syrian dictator and “head of the terror state” Bashar Assad would “go down in history as a war criminal, and regime elements will pay a heavy price for this treacherous attack.”

Mustafa Sentop, speaker of the Turkish parliament, said that while diplomatic efforts to resolve the Idlib conflict would continue, “attacks targeting our country in the field will meet the harshest response.”

“Whatever power or alliance stands against it, Turkey will repay any attacks against it,” Sentop warned, implicitly signaling Turkey’s willingness to fire on Russian forces if provoked.

The Turks did not merely ask for the rest of the world to get involved. They went straight to hardball tactics against the European Union, announcing on Friday that Turkish border patrols will be ordered to stand down and allow a new wave of Syrian refugees dislocated by the fighting in Idlib to flood into Europe. Turkey has long complained that it does not have the resources to deal with the refugees pouring out of Syria.

A large number of Syrian migrants immediately headed for Greece, which responded by increasing border security and declaring it would not allow migrants to enter the country “illegally.”

“Greece does not bear any responsibility for the tragic events in Syria and will not suffer the consequences of decisions taken by others. I have informed the European Union of the situation,” said Greek Prime Minister Kyriakos Mitsotakis on Friday.

Erdogan on Friday said he plans to speak with U.S. President Donald Trump and the leaders of France, Germany, and the United Kingdom about the Idlib crisis. Turkey indicated that it wants American and European help to establish a no-fly zone in Syria.

NATO on Friday expressed concerns about the possibility of an escalating conflict between Turkey and Syria, or even Turkey and Russia, while the U.N. Security Council announced it would hold an emergency meeting to discuss the situation on Friday afternoon.