In accordance with the Astana agreement between Turkey, Iran and Russia, Turkish troops will provide the security inside Syria's Idlib province and Russian troops will ensure security outside of it.
President Recep Tayyip Erdogan said on Sunday that Turkey was implementing a deal agreed with Russia and Iran to reduce violence in Syria's northern province of Idlib.
He said the operation was being conducted in cooperation with Free Syrian Army opposition fighters.
"Now we are applying the Astana decisions in Idlib," Erdogan said, referring to an agreement announced last month in the Kazakhstan capital.
Erdogan said if Turkey had not acted "bombs would fall on our cities."
"Our efforts in Idlib are going on, in cooperation with the Free Syrian Army, without problems at the moment," he told members of his ruling AK Party at a meeting in the western Turkish province of Afyon.
TRT World’s Sarah Firth reports with more from the Turkish border city of Antakya.
Focus on Hayat Tahrir Al Sham
Idlib had been a centre of fighting between Russia and Iran-backed regime forces and Turkey-backed opposition forces until July this year when Hayat Tahrir Al Sham took control of a large part of the province.
Hayat Tahrir Al Sham alliance is led by Jabhat Fateh al Sham, or the Nusra Front, which publicly shed its status as al Qaeda's Syrian affiliate in 2016 and rebranded to head the Hayat Tahrir al Sham amalgam.
The US maintains that the group is still linked to Al Qaeda, however.
The alliance controls most of the northwestern province of Idlib after expelling former allies earlier this year.
The group on Saturday decried the operation saying it would "not be a picnic" for the FSA.
"The lions of jihad and martyrdom are waiting to pounce on them," it added in a statement posted on a social media site.
Idlib has strategic importance for all parties involved in Astana deal, and has shown little signs of de-escalation.
According to the agreement on the Idlib de-escalation zone, Russia's military policemen will maintain security outside Idlib and Turkey will deploy its troops inside Idlib.
Earlier this week, sources from Turkey-backed opposition in Idlib, who spoke to TRT World on condition of anonymity, said that Iranian observers will be positioned along the southern borders of Idlib to create a practical buffer zone between Syrian regime forces and the opposition forces.