A Syrian government air strike aiming to stop a Turkish convoy reaching a rebel-held town in northern Syria has killed three civilians, Turkey alleges.
Another 12 people were injured in the attack in Idlib province on Monday, the Turkish defence ministry said.
Idlib is one of the few areas in Syria not under government control, reports BBC.
Syria has condemned the convoy, which is laden with ammunition. Turkey - which supports the rebels - says the strike violates previous agreements.
The agreement - reached last September between Russia and Turkey - should mean Idlib is protected from a major government offensive.
But in recent weeks government forces have stepped up their assault on the region - the last major anti-Assad stronghold - killing hundreds of civilians and driving hundreds of thousands from their homes.
On Sunday evening a Russian-backed government offensive reached Khan Sheikhoun, the rebel stronghold where the Turkish convoy is headed.
The convoy, which is reportedly made up of armoured vehicles, entered the region on Monday, but the attack has forced it to stop on a highway north of the town.
The UK-based Syrian Observatory for Human Rights (SOHR) reported that Russian aircraft had carried out strikes near a Turkish convoy in northern Syria on the morning of 19 August.
The convoy's arrival has been condemned in Syrian state media as an act of aggression. It said the munitions would not stop government forces "hunting the remnants of terrorists".
The incident has raised fears of direct clashes between the countries.
What's happening in Syria?
After eight years of war, the Syrian government is trying to win back control of the last rebel-held areas.
Government forces, backed by Russia, reportedly entered the northwest outskirts of Khan Sheikhoun on Sunday.
Khan Sheikhoun, which was hit by a Sarin gas attack in 2017, is a strategically important town in the south of the province.
Syrian forces have now massed to both the east and west of Khan Sheikhoun, and air strikes are targeting the centre and surrounding villages.
Last week a Syrian government war plane was shot down in the area, hit by an anti-aircraft missile fired by militants, according to Syrian state news agency Sana.
Jihadist group Hayat Tahrir al-Sham (HTS) has claimed responsibility and released footage purportedly showing the captured pilot.
A colonel from a rebel faction confirmed to Reuters news agency that there were battles going on on the outskirts. Fighters from a Turkish-backed rebel force have joined the defence, he said.