Air strikes hit positions near a Turkish convoy which was stuck at a highway in northwest Syria after crossing into Idlib province on Monday, the Syrian Observatory for Human Rights said.
The British-based war monitoring group said one fighter from a Turkey-backed faction accompanying the convoy was killed and others were injured.
A Turkish military convoy was attacked en route to one of its observation posts in northwest Syria on Monday, Turkey's Defence Ministry said, adding that three civilians were killed and 12 others wounded in the air strike.
The ministry said in a statement that the attack violated Ankara's agreements and cooperation with Russia, Syrian President Bashar al-Assad's most powerful ally. It said Russia had been told in advance about the convoy.
Syria strongly condemned the entry of the Turkish convoy carrying ammunition, weapons and equipment through the Syrian-Turkish border on their way to Khan Sheikhun, according to the Syrian SANA news agency.
On Sunday, the Syrian army entered the city of Khan Sheikhun in the Idlib province for the first time since they lost control of the city five years ago, according to the Iranian Fars news agency. Heavy battles are taking place in and around the city.
Many rebels were killed or wounded during attempts by the Syrian army to enter the city, according to SANA.
Khan Sheikhun is a important strategic point as it links east, west and north Idlib. Conquering the city would aid the Syrian army in taking over Mara'at al-Na'man and in taking control of the Aleppo-Damascus international link road.
An official at the Syrian Foreign and Expatriates Ministry told SANA that the Turkish convoy was on its way "to help the defeated terrorists of Jabhat al-Nusra which is on the lists of the Security Council as a terrorist organization, which affirms again the continued unlimited support provided by the Turkish regime to the terrorist groups."
"The Syrian Arab Republic strongly condemns this flagrant Turkish violation and it holds the Turkish Regime fully responsible for the consequences of this stark violation of the sovereignty and the territorial integrity of the Syrian Arab Republic which constitutes an outrageous breach of the international law’s provisions," added the official.
"This aggressive behavior by the Turkish regime will not in any way affect the determination of the Syrian Arab Army to continue to hunt down the remnants of terrorists in Khan Sheikhoun and other areas till liberating every inch of the Syrian territories from terrorism," concluded the official.
Reuters contributed to this report.