AMMAN: Turkish military personnel entered northwestern Syria and met with members of a hardline Islamist alliance on Sunday, rebel officials told Syria Direct, one day after the Turkish president announced a “landmark” military operation there.

On Sunday morning, a “Turkish military convoy” entered rebel-held territory in northwestern Aleppo province. There, Turkish personnel met with members of the alliance Hay’at Tahrir a-Sham (HTS), an official with HTS told Syria Direct.

The official spoke on condition of anonymity because he is not authorized to make statements about the meeting, which took place in the HTS-held Aleppo town of Darat Izza, 15 kilometers from the Turkish border.

A commander with rebel forces opposed to HTS, a local Civil Defense spokesman and a media activist in Darat Izza who saw the convoy confirmed to Syria Direct that Turkish military vehicles entered the Aleppo province town on Sunday.

"Negotiations took place" at Sunday morning's meeting, according to the HTS official, who declined to elaborate on the content of the meeting.

Darat Izza sits in a part of opposition-held rural Aleppo immediately east of rebel bastion Idlib province.

The reported talks come one day after Turkish President Recep Tayyip Erdogan announced that a “landmark operation” by Ankara-backed Syrian rebels was underway in Idlib province and that Turkish forces would participate.

The operation, he told attendees at a political conference in the Turkish city of Afyonkarahisar on Saturday, is aimed at preventing a "terror corridor" along Syria's northwestern border with Turkey.

Pro-Ankara Syrian rebel fighters drive from northern Aleppo to Idlib on Oct. 6. Nazeer al-Khatib/AFP.

Idlib is the largest Syrian province still under rebel control, and is home to an estimated two million residents—many of whom fled there from elsewhere in Syria. HTS—led by former Al-Qaeda affiliate Jabhat Fatah a-Sham—controls the vast majority of the province.

Last month, an agreement between Turkey, Russia and Iran in Astana, Kazakhstan made the largely HTS-controlled Idlib province—as well as parts of neighboring Aleppo, Hama and Latakia provinces—the fourth and final “de-escalation zone” in Syria to be implemented since the three powers first announced the plan in May.

Under the terms of September’s Astana agreement, “checkpoints and observation posts” manned by Turkish, Russian and Iranian forces were to be established along the borders of rebel-held Idlib province to prevent further battles, according to a statement released by Turkey’s Ministry of Foreign Affairs.

The agreement did not include HTS, a longtime opponent of the Astana talks. In response, the rebel alliance launched a military offensive against regime forces in northern Hama province, to “demolish and defeat the negotiations that happened at the Astana conference,” an HTS source told Syria Direct at the time.

Turkish intervention in support of the de-escalation zones, then, would appear to invite conflict with HTS. It is in that context that Sunday’s meeting between the two parties took place in Aleppo province, even as Ankara-backed personnel and military vehicles reportedly amassed on the border between Turkey and rebel-held territory in Aleppo and Idlib provinces.

As of Sunday afternoon local time, no Turkish ground forces had entered Syrian territory in Idlib, Mahmoud Faisal, the citizen journalist in Darat Izza, added.

Speaking to reporters at Saturday’s conference in Afyonkarahisar, Turkish Foreign Minister Mevlut Cavusoglu maintained Ankara’s goal is to “prevent conflict” in Idlib province, which borders southern Turkey just west of neighboring Aleppo province.

Prime Minister Binali Yildirim stated the same day that Turkish forces would “ensure safety in Idlib, and will cooperate with Russia.”

On Sunday afternoon, Russian government officials had not yet commented on the Turkish-backed military operation in Idlib.

Increased Turkish presence in Idlib and Aleppo would also work to prevent what Erdogan called on Sunday “the establishment of a new terror state at our border,” that is, to forestall expansion by Kurdish forces which control a 115-kilometer stretch of the Syrian border with Turkey in northwestern Aleppo province.

The operation comes more than one year after a Turkish-backed campaign—dubbed Euphrates Shield—launched in August 2016 to drive out the Islamic State from territory south of the Turkish border. That offensive, fought by FSA and Turkish ground forces, also aimed to limit Kurdish territorial ambitions in the same area.