ISTANBUL (Reuters) - A Turkish soldier was killed in Syria’s Idlib region in a bomb attack by Russian-backed government forces, the defence ministry said on Saturday, Turkey’s 16th military death during a month in which talks between Ankara and Moscow have stalled.

The rising Turkish military death toll, including two on Thursday, could complicate a possible deal to halt a spike in fighting in Syria’s northwest. Since early December nearly a million Syrians, mostly women and children, have been displaced in the winter cold there.

Turkish President Tayyip Erdogan said he will meet Russian, German and French counterparts on March 5 to discuss Idlib, where Syrian government forces are pushing to retake the last large rebel-held region after nine years of war in the country.

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

Turkish forces retaliated to the bomb attack Saturday and destroyed 21 “regime targets”, the ministry said, adding the soldier was a tank mechanic who died when transferred to hospital.

After Russian and Turkish delegations failed to reach an agreement in the last two weeks, Erdogan has promised to push back Syrian government forces if they press on.

Turkey has “determined our road map” for Syria after calls on Friday with Vladimir Putin, Angela Merkel and Emmanuel Macron, Erdogan told supporters in Izmir on Saturday. “I expressed our determination clearly” to them, he said.

The German and French leaders expressed concern about the humanitarian situation in Idlib and urged an end to the conflict, while the Kremlin has said it is discussing the possibility of holding a four-way summit.

In Damascus, the transport ministry declared the main highway from Aleppo running through Idlib open to the public after it was recaptured in the offensive.

Taking back the M5 highway from insurgents marks a big gain for President Bashar al-Assad, as it restores state control over the route between Syria’s two biggest cities for the first time in years of conflict.

Syrian state media, citing a military source, said any breach of Syria’s airspace “will be dealt with as an enemy military target”. Damascus and Ankara, which opposes Assad, have agreed Russia could control Idlib airspace.

The United Nations has warned fighting in Idlib could “end in a bloodbath” and called for a ceasefire. The latest Syrian offensive has prompted the biggest civilian exodus in a civil war that has killed an estimated 400,000 Syrians, displaced millions more and left much of the country in ruins.

Separately in Syria’s northeast, the UN has suggested that the Tal Abiyad border crossing between Syria and Turkey could be used to deliver aid to civilians after Russia and China blocked the world body from using a crossing point on the Iraqi border to provide help.