As NATO ambassadors met on Friday in Brussels in an emergency session and European leaders called for calm, Mr. Putin spoke by telephone with Mr. Erdogan in an effort to calm tensions. Mr. Trump also spoke by telephone with Mr. Erdogan and the leaders promised “additional steps to prevent the great humanitarian catastrophe unfolding in the Idlib region,” according to the Turkish government.

Asli Aydintasbas, a senior fellow with the European Council on Foreign Relations, said NATO would offer “plenty of moral support” to Turkey but that “no one wants to get militarily entangled with Russia.” This, she added, meant that “Erdogan will have to fix this with Putin.”

Russia said on Friday that it was sending two warships equipped with Kalibr cruise missiles toward Syria’s coast in the eastern Mediterranean, but insisted that its forces had played no role in the attack on Turkish troops. That contradicted reports from the scene that described a Russian jet striking a Turkish convoy, and then artillery strikes pounding Turkish troops in several buildings.

Mr. Putin’s spokesman, Dmitri Peskov, sought to calm tempers in his daily briefing on Friday, insisting that Russia had honored a pledge to safeguard Turkish observation posts near Idlib. He said no Turkish servicemen had been hurt in these outposts, while suggesting that it was Turkey’s fault that some of its troops strayed beyond these designated areas into territory controlled by rebels.

“The tragic instances of deaths among Turkish personnel happened in the areas where terrorist gangs were conducting offensive operations,” Mr. Peskov said.

Turkish planes, artillery and drones retaliated after the attack, pounding Syrian government positions. “Our operations will continue until the bloody hands laid on our soldiers are broken,” said Hulusi Akar, Turkey’s defense minister.

While he avoided placing direct blame on Russia, Mr. Akar noted that Thursday’s attack had been carried out even though Turkey had coordinated the location of its troops with Russian forces on the ground. He also said there were no rebel groups near the scene of the attack, as the Kremlin asserted.