ANKARA — DHA news agency reported some 300 Syrian, Iranian, Iraqi, Moroccan and Pakistani refugees were gathering at the border with Greece, while others gathered on beaches facing Greek islands off Turkey’s western coast.

On Friday morning, broadcaster NTV showed images of dozens of people carrying rucksacks, suitcases and plastic bags, crossing fields towards the Greek frontier.

Near the Pazarkule border crossing with Greece, Turkish police stopped some 150 refugees about one kilometer (half a mile) from the border, preventing them from going further.

A Greek police official said dozens of people had gathered on the Turkish side of the Greek-Turkish land border shouting “open the borders.” Greek joint police and military border patrols were deployed on the Greek side to prevent any illegal crossings. The official spoke on condition of anonymity as they were not authorized to speak on the record.

Turkey hosts some 3.6 million Syrians and under a 2016 deal with the European Union agreed to step up efforts to halt the flow of refugees to Europe. Since then, Erdogan has repeatedly threatened to “open the gates” in several disputes with European states.

Omer Celik, spokesman for Erdogan’s ruling party, said Turkey was “no longer able to hold refugees” following the Syrian attack — reiterating a standing threat by Ankara.

Turkey on Friday raised the death toll from a Syrian government airstrike on its forces in northwestern Syria the previous night to 33 Turkish troops, the highest number of Turkish soldiers killed in a single day since Ankara first intervened in the Syrian conflict in 2016.

The deaths, which came in an attack late Thursday, were a serious escalation in the direct conflict between Turkish and Russia-backed Syrian forces that has been waged since early February. The earlier reported death toll was 29 troops.

Ambassadors from NATO countries were holding emergency talks on Friday at the request of Turkey, a member of the alliance. The Turkish stock market fell 10% in the wake of the airstrike, while the Turkish lira slid against the dollar.

Rhami Dogan, the governor of Turkey’s Hatay province bordering Syria’s Idlib region, said 32 troops wounded in the attack were being treated in hospitals. Turkey has had 54 soldiers killed in Syria’s northwestern Idlib province since the beginning of February, including the latest fatalities.

Turkey is a main backer of the Syrian opposition while Russia has been giving military support to the weeks-long Syrian government offensive in Idlib that has displaced about 950,000 people and left hundreds of civilians dead.

Russia’s Defense Ministry said Friday the Turkish troops that came under fire in Idlib were deployed among “terrorist battle formations.” They were in the area of Behun, and according to coordinates given to Russia’s Reconciliation Center in Syria, “there were no Turkish military units in the area … and there weren’t supposed to be,” the ministry said,

Russian air forces did not carry out airstrikes in the area, the statement added, and after receiving information about Turkish casualties, “the Russian side took all the necessary measures in order for the Syrian forces to stop the fire.”

Meanwhile, two Russian frigates carrying cruise missiles have been deployed to Syria, Russian navy officials Friday. Admiral Makarov and Admiral Grigorovich of the Black Sea Fleet are currently en route to the Syrian coast with Kalibr cruise missiles on board. Both warships previously took part in Russia’s offensive in Syria.

Syrian state news agency, SANA, carried a brief report saying Turkey has acknowledged its forces were killed “in operations of the Syrian Arab Army against a terrorist organization,” adding that Syrian troops at the time were repelling attacks by “terrorist groups backed by Turkey.”

U.N. secretary-general reiterated his call for an immediate cease-fire and expressed serious concern about the risk to civilians from escalating military actions,” U.N. spokesman Stephane Dujarric said.

“Without urgent action, the risk of even greater escalation grows by the hour,” he said.

Turkish President Recep Tayyip Erdogan held a six-hour emergency security meeting in Ankara late on Thursday, the Anadolu news agency reported. Turkish Foreign Minister Mevult Cavusoglu spoke to NATO Secretary General Jens Stoltenberg by telephone while Erdogan’s spokesman Ibrahim Kalin, who plays a senior role in foreign affairs, spoke to U.S. National Security Advisor Robert O’Brien.

The Syrian Observatory for Human Rights, a war monitoring group, said after the attack on Turkish troops, Turkey’s armed forces shelled Syrian army positions in different parts of Idlib, killing at least 16 soldiers. It gave no further details and there was no comment from Syria’s state media.

In recent weeks Turkey has sent thousands of troops as well as tanks and other equipment to Idlib. As recently as Wednesday, Erdogan gave the Syrian government until the end of February to pull back from its recent advances or face Turkish “intervention”.

Idlib is the final stronghold of fighters opposed to Syrian President Bashar Assad. Turkey provides some of the militants with direct support and has accused Syria of breaking a 2018 agreement to reduce the conflict in Idlib. Russia and Assad have said Turkey has failed to honor a deal to separate extremist groups from other fighters in the region.

The situation in Idlib “threatens our national survival” said Devlet Bahceli, who heads the nationalist party allied to Erdogan’s government.

The airstrike came after a Russian delegation spent two days in Ankara for talks with Turkish officials on the situation in Idlib, where a Syrian government offensive has sent hundreds of thousands of civilians fleeing towards the Turkish border. The offensive has also engulfed many of the 12 military observation posts Turkey has in Idlib.

After the airstrike, angry crowds gathered outside the Russian consulate in Istanbul, Anadolu said. Standing in front of a line of riot police and a water cannon, they chanted “Murderer Russia, murderer (Russian President Vladimir) Putin.”

The airstrike came after Turkey-backed Syrian opposition fighters retook a strategic northwestern town from government forces on Thursday, opposition activists said, cutting a key highway just days after the government reopened it for the first time since 2012.

Despite losing the town of Saraqeb, Syrian President Bashar Assad’s forces made major gains to the south. Assad now controls almost the entire southern part of Idlib province after capturing more than 20 villages Thursday, state media and opposition activists said. It’s part of a weekslong campaign backed by Russian air power into Syria’s last rebel stronghold.

Defense Minister Hulusi Akar and the commanders of Turkey’s army and air force went to the Syrian border Friday.