Turkish President Recep Tayyip Erdogan has said he will meet the leaders of Russia, France and Germany next month to discuss the situation in northwest Syria, where a military push by Moscow-backed government forces against the last opposition-held enclave has displaced nearly a million people.

His comments on Saturday came as the Turkish defence ministry said a Turkish soldier had been killed in Syria's Idlib province in a bomb attack by government forces, becoming Turkey's 16th military death during a month in which talks between Ankara and Moscow have failed to de-escalate a recent spike in fighting.

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Speaking to reporters in Izmir, Erdogan did not specify where the March 5 meeting would be held. He added, however, that Turkey "determined our road map" for Syria after calls on Friday with Russian President Vladimir Putin, German Chancellor Angela Merkel and French President Emmanuel Macron.

"I expressed our determination clearly" to them, said Erdogan, who last week threatened an "imminent" operation against Syrian forces in the region.

Turkey has sent thousands of troops and equipment to the region just south of its border to head off the government forces' campaign driven by Russian air raids. Already hosting some 3.7 million Syrian refugees, it says it cannot handle another wave and has closed its borders.

Macron and Merkel on Friday expressed concern about the humanitarian situation in Idlib and urged an end to the conflict, while the Kremlin said it was discussing the possibility of holding a four-way summit.

The Turkish president told Putin over the phone on Friday that the solution was to return to the Sochi agreement they signed in 2018, which allowed Turkey to establish military posts across Idlib designed to prevent a Syrian government assault.

That deal has been increasingly set aside as Russian-backed Syrian forces advance steadily into the region, the final stronghold of rebels fighting Syrian President Bashar al-Assad's government during a nine-year war that has killed hundreds of thousands of people and displaced millions.

The United Nations warned on Friday that an escalation in fighting could end in a "bloodbath" and called for an immediate ceasefire. Nearly 900,000 people, more than half of whom are children, have fled their homes since December 1, when the Russian-backed Syrian government forces pressed ahead with their military offensive,

Separately, Turkey's defence ministry said its forces retaliated to the "despicable" bomb attack that killed the soldier, destroying 21 Syrian government targets. It said the soldier was a tank mechanic who died when transferred to hospital.

The incident came two days after two Turkish soldiers were killed in an air raid in Idlib, which Ankara blamed on Syrian government forces.

Earlier this month, 13 Turkish soldiers were killed in Syrian attacks, prompting Erdogan to say Turkey will attack Syrian forces "anywhere" in Syria if another soldier was hurt.

Syrian troops have reconquered swathes of Idlib and retaken the strategic M5 highway connecting the country's four largest cities, as well as the entire surroundings of Aleppo city for the first time since 2012.

On Saturday, the highway opened for public use for the first time in nearly eight years, the transport minister said.