Turkish troop reinforcements entered Syria's opposition bastion of Idlib on Tuesday (September 25th), AFP reported, a week after a deal between Ankara and Moscow averted a government offensive.
Around 35 military vehicles travelled south down the main highway near the town of Saraqib after midnight.
The convoy was accompanied by pro-Ankara opposition forces of the National Liberation Front (NLF), who control part of the enclave on the Turkish border.
The Syrian Observatory for Human Rights said the forces deployed to several Turkish positions around the northwestern province.
Since last year, Turkish troops have manned 12 monitoring positions in the opposition zone under a de-escalation agreement between Turkey, Russia and fellow regime ally Iran.
Last week, Ankara and Moscow announced a new agreement for a demilitarised zone along the horse-shoe shaped front line between the opposition fighters and government troops.
Extremist alliance Tahrir al-Sham controls more than half of the opposition zone, while NLF fighters hold sway over most of the rest.
The agreement gives Turkey the responsibility to ensure that all fighters in the planned demilitarised zone hand over their heavy weapons by October 10th and that the more radical among them withdraw by October 15th.
The agreement also provides for Turkish and Russian troops to patrol the buffer zone.
Meanwhile, hundreds of "Islamic State of Iraq and Syria" (ISIS) fighters arrived Monday on the outskirts of Idlib under a regime transfer from the east of the country.
The extremists were ferried overnight from the eastern province of Deir Ezzor near the Iraqi border, said the Observatory.
"Regime forces transported more than 400 ISIS fighters late Sunday from the desert near the town of Albu Kamal," the monitor said.
They arrived in the eastern countryside of Idlib province at dawn on Monday, near areas where other extremist groups are present, it said.
Observers have already warned that Turkey's task was almost impossible and the presence of ISIS, over which it has very limited sway, will further muddy the waters.
Tore Hamming, a Copenhagen-based academic specialised in the study of extremist groups, argued that the ISIS transfer could spark clashes between rival factions inside Idlib.