File photo of Russian President Vladimir Putin. Photograph:( AFP )
In 2018, Russia and Turkey agreed a memorandum to enforce a demilitarised zone in Syria's Idlib region from which "radical" fighters would be required to withdraw.
Russian President Vladimir Putin's spokesman Dmitry Peskov said the Turkish side "had taken upon itself an obligation to neutralise terrorist groups" in Idlib under an agreement between Ankara and Moscow from 2018.
But "all these groups are mounting an attack on the Syrian army from Idlib and are acting aggressively towards Russian military installations", he told reporters.
"This is unacceptable and runs counter to the Sochi agreements," he said, referring to the 2018 deal between Russia and Turkey.
At the same time, Peskov sought to defend the Syrian army, saying it targeted "terrorists" and not civilians.
Also read: Turkey reinforces troops in Syria's Idlib
He said the Kremlin had no current plans to communicate with Syrian President Bashar al-Assad but said the two countries' armed forces were in contact.
Russia insists, however, that groups of "terrorists" continue fighting in Idlib.
Despite being on opposite sides of the war, Damascus ally Moscow and rebel supporter Ankara have worked closely to resolve the conflict.
Earlier Wednesday, the two discussed de-escalation of the Syrian crisis by phone.
"The importance was noted of the full implementation of existing Russian-Turkish agreements including the Sochi memorandum," the Kremlin said after the Putin-Erdogan phone call.
Erdogan on Wednesday threatened to strike Syrian regime forces "everywhere" if his soldiers were harmed and accused Russia of committing "massacres" in Idlib.
He said Turkey would act "from now on regardless of the Sochi deal".
Syria's Russia-backed government forces launched an all-out assault on Idlib in December, retaking town after town. Hundreds of thousands have fled and hundreds of civilians have been killed.