Turkey's military says that three Turkish soldiers have been killed and 10 others wounded in Syria in an air strike thought to have been carried out by Syrian government forces.
The air strike occurred before dawn on November 24 in the course of a Turkish-led Syrian rebel operation in northern Syria, said a statement from the armed forces posted on its website.
Earlier, Turkish media reported that the attack in the Al-Bab region was carried out by Islamic State (IS) militants.
The army statement said the wounded troops were evacuated from the area. One of the wounded soldiers was said to be in critical condition.
The incident is likely to further escalate tensions between Ankara and Damascus.
On August 24, Turkey sent ground troops into northern Syria to support Syrian opposition forces in the fight against IS militants and to curb Syrian Kurdish territorial gains.
Turkish President Recep Tayyip Erdogan said this week that the Syrian rebels backed by the Turkish military were pushing forward with the aim of taking Al-Bab from IS militants after liberating Jarabulus, Al-Rai, and Daniq from the extremist group.