The incident marks the first time Turkish soldiers are thought to have been killed by Syrian regime forces since the start of Operation Euphrates Shield.
An air strike thought to have been carried out by Syrian regime forces killed three Turkish soldiers overnight and wounded 10 others, the Turkish military announced on Thursday. One soldier remains in critical condition.
It would be the first time Turkish soldiers are known to have been killed by Syrian regime forces in the offensive, dubbed Euphrates Shield, which was launched on August 24.
Operation Euphrates Shield is aimed at degrading the Daesh and PKK presence on the Syrian side of Turkey's border.
The attack occurred at around 3:30 local time (0030 GMT) in the course of a Turkish-led Syrian rebel operation in northern Syria, the army statement said. The wounded soldiers were said to have been rapidly transferred to hospitals along the Turkish border provinces of Kilis and Gaziantep.
There have been several incidents in the recent past between the Assad regime and Turkey. Syria downed a Turkish jet in 2012, and in 2014 Turkish fighter jets shot down a Syrian warplane.
Earlier, security and hospital sources in Turkey said Daesh had carried out the attack, according to Reuters.