Turkey has reportedly returned fire after a shell fired from Syria landed on its territory close to their common border.
Turkey's state-run Anadolu Agency said the shell from Syria came down near the Turkish village of Asagipulluyaz in Hatay province.
It quoted the province's governor as saying that Turkish troops "responded with fire" after the mortar landed in a rural area. No one was reported hurt.
Turkish artillery has fired at targets in Syria for two days after a mortar from Syria killed five civilians in a Turkish border town.
Turkey's parliament also voted on Thursday to allow cross-border military operations in Syria. Turkey, a member of Nato, preserves its right to hit back if shelling continues, Turkish officials have warned.
The US has expressed support for Turkey's response.
"The United States condemns the violence and the aggressive actions of the Syrians," White House spokesman Josh Earnest told reporters.
"The Turks have taken some actions that are designed to ensure that their sovereignty is no longer violated by Syrian aggression and we stand shoulder-to-shoulder with them as they take those actions. They are certainly appropriate."
The uprising against Syrian President Bashar al Assad began in March 2011 and has gradually developed into a bloody civil war - estimated to have killed more than 30,000 people.