The Turkish Armed Forces are clearly instructed," Turkish Prime Minister Ahmet Davutoglu told Turkish TV. "Even if it is a flying bird, it will be intercepted."
But he played down the possibility of a "Turkey-Russia crisis", saying that channels between the two countries remained open.
UN spokesman Stephane Dujarric expressed concern at the dangers of having "a lot of different countries and different coalitions" carrying out air campaigns in Syria, saying the situation was "fraught with danger". He urged a renewed focus on a political solution to the conflict.
The Russian air campaign began on Wednesday, with Moscow saying it was targeting IS positions and those of other Islamist groups. Syria said on Monday