The Turkish Army suffered mass casualties in the strike, officials said, an attack that could set off a direct conflict between Turkey and Russia.
ISTANBUL — The Turkish Army suffered mass casualties in an airstrike in northwest Syria late Thursday, an attack that could dramatically change the course of the Syrian war as fears grow of a direct conflict between Russia and Turkey, a NATO member.
At least 33 Turkish soldiers were killed and more than 30 wounded, said Rahmi Dogan, the Turkish governor of the southern province of Hatay, where the Turkish casualties were arriving.
Turkish officials said the strike had been carried out by Syrian government forces, but Russian jets have been conducting most of the airstrikes in the area in recent weeks. Turkish protesters in Istanbul converged on the Russian Consulate there early Friday, chanting “Murderer Russia! Murderer Putin!”
Turkish officials have avoided blaming the Russian government for aggression against their forces in Syria, hoping to avoid a direct confrontation with Russia’s much stronger military and to keep a line open for talks with Russia’s president, Vladimir V. Putin.
Russian officials could not be reached for comment late Thursday.
President Recep Tayyip Erdogan of Turkey convened an emergency meeting Thursday evening in Ankara, Turkish media reported. And Turkish forces began retaliating Thursday against Syrian forces in northeastern Idlib Province.
Turkey has long supported opposition forces in Syria’s nine-year civil war against the government of President Bashar al-Assad. Mr. Assad, backed by Russia and Iran, has largely defeated the uprising, at a cost of hundreds of thousands of lives and the creation of millions of refugees.
His government, backed by Russian warplanes, is fighting in Idlib to retake the country’s last rebel-held province. In the past three months, the intensified fighting there has driven nearly a million people from their homes, creating a humanitarian crisis on Turkey’s border.
In recent days, tensions between the two sides have been rising, increasing fears of a war breaking out between Turkey and Russia, which controls the airspace in northwestern Syria.
Mr. Erdogan has called for Syrian government and Russia forces to cease their offensive in Idlib and to pull back from Turkish positions, which have been encircled and cut off by Syrian government forces. He has also called for a Turkish-controlled safe zone in the region for the displaced civilians.
Turkey has deployed thousands of troops into the province to stem the Syrian government advance but has been severely hampered by the lack of air support. Russia has been conducting a blistering air campaign across the province, bombing hospitals, schools and residential buildings, killing at least 300 people in three months.
Turkey has asked the United States for Patriot missiles to help defend its troops, and called for NATO to enforce a no-fly zone to protect the nearly three million civilians in Idlib Province.
But Washington and NATO members have so far refused to engage militarily in northwest Syria out of reluctance to confront Russia, Western officials said. The United States is withholding Patriot missiles until Turkey agrees to render its Russian S400 missile system inoperable.
The United States has about 500 troops in northeastern and southern Syria, whose main missions are to prevent the Islamic State from returning there and to guard Syrian oil fields.
Turkey is a NATO member, prompting fears in the West that an attack on Turkey could require a response by allies in Europe and North America, dramatically escalating Syria’s already complex war.
“The attack against Turkey is an attack against NATO,” Omer Celik, the spokesman for Mr. Erdogan’s Justice and Development Party, said on the CNN Turk news channel. “NATO should have been with Turkey, not starting today but from before these events. We are expecting concrete actions on the safe zone and no-fly zone.”
There was no immediate comment from the White House, but President Trump has made it clear that he would like to keep out of the conflict, and has previously ordered American troops to leave Syria.
On Wednesday, Defense Secretary Mark T. Esper told members of the House Armed Services Committee that the United States was not looking to reassert its presence there.
“There has not been that discussion about re-engaging in the civil war,” he said. “We think the best path forward is through the U.N. process that is underway.”
Several American officials, however, reacted to the airstrike on Thursday with alarm.
“The prospects of a direct military confrontation between Turkey & Russia in Syria are very high & increasing by the hour,” Senator Marco Rubio, Republican of Florida, said in a tweet. Mr. Erdogan, he said, “is on the right side here. Putin & Assad are responsible for this horrific humanitarian catastrophe.”
Kay Bailey Hutchison, the American ambassador to NATO, told reporters in Washington on Thursday that “everything is on the table.”
“This is a big development,” Ms. Hutchison said, “and our alliance is with Turkey, it is not with Russia.” She added, “We want Turkey to understand that we are the ones that they’ve been allied with.”
The attack on Thursday hit Turkish troops between the towns of Al Bara and Balyoun, south of the city of Idlib. Turkish troops have been positioned in 12 observation posts set up over a year ago as part of a de-escalation agreement with Russia.
A Turkish military convoy traveling to resupply troops came under aerial attack first, and then a building where the troops were based was struck, Abu Yahya, a senior official of the Turkish-backed Syrian fighting force in Idlib Province, said in an interview.
The Turkish-backed Syrian fighters have made significant gains in battles against Syrian government forces farther east recently. They captured the town of Saraqib on the main M5 highway through the province on Wednesday and were engaged in fierce battles farther south on Thursday.
The Turkish Army called on its Syrian proxies to raise their readiness for operations, a Syrian media group reported.
Emotions were running high in Reyhanli, on the Turkish side of the Syrian border, where the casualties were brought. People gathered to donate blood and a crowd chanted “God is Great” outside the main hospital.
The escalation came as Western members of the United Nations Security Council in New York implored Russia and Syria to decree a humanitarian cease-fire in the Idlib region.
“There is more this council can and must do to stop the suffering,” Foreign Minister Heiko Maas of Germany and Deputy Prime Minister Alexander De Croo of Belgium told the council in a joint statement on Thursday morning.
Ursula Mueller, the assistant secretary general for humanitarian affairs, told council members that the deprivations facing civilians in northwest Syria were “not humanly tolerable.” Henrietta Fore, the executive director of Unicef, who is to visit Syria this weekend, said “we desperately need a cessation of hostilities in northwest Syria.”
But the Russians, who have vetoed 14 Security Council resolutions on Syria since the insurgency began in 2011, rejected the entreaty.
Vassily Nebenzia, Russia’s ambassador to the global body, said the only long-term solution in Idlib and the rest of Syria was “a final and irreversible expulsion from the country of all terrorists.”
Idlib’s three million people include about 1.5 million opponents of the Syrian government, who have fled to Idlib from other parts of Syria, as well as fewer than 100,000 jihadists and rebels, according to estimates. The Syrian government and Russia refer to members of the civilian opposition and the rebel and jihadist groups as terrorists.
Russian state news services did not report on the strike by late Thursday, but they cited military officials blaming Turkey for supporting militants who are targeting Russian positions.
“The Turkish side continued to support illegal armed formations with artillery fire and reconnaissance and attack drones,” Interfax cited a rear admiral, Oleg Zhuravlev, as saying. Admiral Zhuravlev said the Russian Air Force shot down a Turkish drone.
Rossiya 24, a state news channel, reported that Turkey was targeting Syrian Army troops with artillery and Russian helicopters with antiaircraft fire in response to the strike that killed Turkish soldiers. The report cited only unspecified “information” it had received, not an official source.
Reporting was contributed by Saad Alnassife from Gaziantep, Turkey; Lara Jakes and Zach Montague from Washington; Hwaida Saad from Beirut; Rick Gladstone from New York; and Andrew Kramer from Moscow.