(Reuters) - A small Turkish army reconnaissance team crossed the border into Syria's Idlib province on Sunday, a senior Syrian rebel said, ahead of a planned deployment by Turkish-backed rebels there.
The group of military vehicles was escorted into the area by the rebels' rival, the Tahrir al-Sham jihadist alliance, against which the operation has been planned, local sources said, suggesting a deal might be reached to avert fighting.
However, the jihadists and the Turkish military had earlier exchanged fire nearby, underscoring tensions as Turkey builds up forces and the rebel groups it backs prepare to enter Idlib.
Turkish President Tayyip Erdogan said on Saturday that Syrian rebels backed by Turkish forces would launch an operation in Idlib and warned that Turkey would not allow "a terrorist corridor" near its borders.
Prime Minister Binali Yildirim stressed the importance of ensuring de-escalation near the border. "We will ensure safety in Idlib, and will cooperate with Russia," Yildirim said.
The operation follows a deal between Turkey and Syrian President Bashar al-Assad's allies Russia and Iran to impose a "de-escalation" zone in Idlib and surrounding areas to reduce warfare there, an agreement that did not include Tahrir al-Sham.
A local resident and another local rebel said they had seen Turkish military vehicles enter Idlib and then travel under Tahrir al-Sham escort along a road. The senior Syrian rebel said the reconnaissance team were heading to Sheikh Barakat, a location that overlooks both rebel-held areas of Aleppo province, adjacent to Idlib, and the Kurdish-controlled area of Afrin.
Reuters witnesses, the local resident and local rebel, and the Syrian Observatory for Human Rights, a Britain-based war monitor, said that, earlier on Sunday, the Turkish military and Tahrir al-Sham clashed near the village of Kafr Lusin in Idlib. Tahrir al-Sham fired on a Turkish bulldozer removing sections of a border wall and Turkish artillery returned fire, they said.
The area was later quiet. Rebel groups taking part in the operation -- part of the Euphrates Shield campaign that Turkey has backed with armor and troops in another part of Syria to the east of Idlib since last year -- said on Saturday they expected it to start very soon.
Tahrir al-Sham said any incursion into Idlib would "not be a picnic" for its enemies. Tahrir al-Sham is spearheaded by the former Nusra Front, which was al Qaeda's Syrian branch until last year, when it changed its name and broke formal allegiance to the global movement founded by Osama bin Laden.
It has been a formidable military force since early in the conflict, often fighting alongside other rebel groups, but since early this year it has battled them as it tried to gain control over areas including Idlib.
Idlib and neighboring parts of northwest Syria represent the country's biggest and most populous rebel stronghold, home to more than two million people, many of them refugees from other regions.
Turkey has been one of the biggest supporters of rebels fighting Syrian President Bashar al-Assad during the six-and-a-half-year war, but its focus has moved from ousting him to securing its own border.
Its biggest security concern on the frontier is the powerful Kurdish YPG militia, which as part of a U.S.-backed alliance is fighting Islamic State in eastern Syria. The YPG controls Afrin, one of the areas that the Turkish reconnaissance team will be able to over look from Sheikh Barakat, the senior rebel said.