Turkey has scrambled six F-16 fighter jets near its border with Syria after Syrian helicopters came close to the border.
A statement said six jets were sent to the area in response to three such incidents on Saturday, adding that there was no violation of Turkish airspace.
Last month, Syrian forces shot down a Turkish jet in the border area.
Rrelations between the former allies, which were already tense, were further strained by the incident.
On Friday, Turkey said it had begun deploying rocket launchers and anti-aircraft guns along the border in response to the downing of an F-4 Phantom jet on 22 June.
Prime Minister Recep Tayyip Erdogan earlier warned that Turkey had changed its rules of military engagement and would now treat any Syrian military approaching the border as a threat.
More than 30,000 refugees have enter Turkey since an uprising began against the regime of President Bashar al-Assad.