Turkish President Recep Tayyip Erdogan has accused Russia of committing "massacres" in its support of the Syrian government and threatened to strike Syrian regime forces "everywhere" if its soldiers come under renewed attack.
Erdogan's statement came on February 12 as more Turkish reinforcements arrived on the ground.
Russia hit back and accused the Turks of failing to "neutralize terrorists" in Syria's northwestern province of Idlib -- the rebels' last stronghold in the war-wracked country.
Turkey has reinforced its positions in recent days in Idlib with hundreds of vehicles carrying artillery and soldiers.
The Turkish military has lost 14 soldiers in the past nine days and claims to have killed more than 100 Syrian troops loyal to Syrian President Bashar al-Assad as they try to push them back.
Erdogan's direct criticism of Moscow is a rare move since 2015 when Turkey shot down a Russian fighter jet that had strayed into its airspace.
"The regime, backed by Russian forces and Iran-backed militants, are continuously attacking civilians, committing massacres and shedding blood," Erdogan told a parliamentary meeting of his ruling party.
He said Turkey would do "whatever necessary" to push Syrian forces back.
"I hereby declare that we will strike regime forces everywhere from now on regardless of the Sochi deal if any tiny bit of harm comes to our soldiers at observation posts or elsewhere," Erdogan added.
In return, Russia accused Turkey of failing to honor a 2018 deal, with Kremlin spokesman Dmitry Peskov saying Ankara "had taken upon itself an obligation to neutralize terrorist groups" in Idlib.
And Russia's Defense Ministry said the presence of Turkish troops and armor in Idlib was making the situation there much worse.
Turkey, Russia Trade Accusations Amid Rise In Syria Tensions